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14.12.2010 - Under Pressure The Basic Consequences of Depth and Pressure in Scuba Diving
How does pressure change underwater and how do pressure changes effect aspects of scuba diving such as equalization, buoyancy, bottom time, and the risk of decompression sickness? Review the fundamentals of pressure and scuba diving, and discover a concept no one told me during my open water course: that pressure changes more rapidly the closer a diver is to the surface.
The Basics
• Air Has Weight
Yes, air actually has weight. The weight of air experts pressure on your body - about 14.7 psi (pounds per a square inch). This amount of pressure is called one atmosphere of pressure because it is the amount of pressure the earth's atmosphere exerts. Most pressure measurements in scuba diving are given in units of atmospheres or ATA.
• Pressure Increases With Depth
The weight of the water above a diver exerts pressure on his body. The deeper a diver descends, the more water he has above him, and the more pressure it exerts on his body. The pressure a diver experiences at a certain depth is the sum of all the pressures above him, both from the water and the air.
• every 33 feet of salt water = 1 ATA of pressure
• pressure a diver experiences = water pressure + 1 ATA (from the atmosphere)
Total Pressure at Standard Depths*
Depth / Atmospheric Pressure + Water Pressure / Total Pressure
0 feet / 1 ATA + 0 ATA / 1 ATA
15 feet / 1 ATA + 0.45 ATA / 1 .45 ATA
33 feet / 1 ATA + 1 ATA / 2 ATA
40 feet / 1 ATA + 1.21 ATA / 2.2 ATA
66 feet / 1 ATA + 2 ATA / 3 ATA
99 feet / 1 ATA + 3 ATA / 4 ATA
*this is only for salt water at sea level
• Water Pressure Compresses Air
Air in a diver's body air spaces and dive gear will compress as pressure increases (and expand as pressure decreases). Air compresses according to Boyle's Law.
• Boyle's Law: Air Volume = 1/ Pressure
Not a math person? This means that the deeper you go, the more air compresses. To find out how much, make a fraction of 1 over the pressure. If the pressure is 2 ATA, then the volume of the compressed air is ½ of its original size at the surface.
Pressure Effects Many Aspects of Diving
Now that you understand the basics, let's look at how pressure effects four basic aspects of diving.
1. Equalization
As a diver descends, the pressure increase causes the air in his body's air spaces to compress. The air spaces in his ears, mask, and lungs become like vacuums as the compressing air creates a negative pressure. Delicate membranes, like the ear drum, to be sucked into theses air spaces causing pain and injury.
On ascent, the reverse happens. Decreasing pressure causes the air in a diver's air spaces to expand. The air spaces in his ears and lungs experience a positive pressure as they become overfull of air. In a worst case scenario this could burst a diver's lungs or eardrums! This the reason that a diver should never hold his breath underwater - if he holds his breath and ascends even a tiny bit, he could over-expand his lungs.
To avoid a pressure related injury (such as an ear barotrauma) a diver must equalize the pressure in his body's air spaces with the pressure around him.
• To equalize his air spaces on descent a diver adds air to his body airspaces to counteract the "vacuum" effect by
- breathing normally, this adds air to his lungs every time he inhales
- adding air to his mask by breathing out his nose
- adding air to his ears and sinuses by using one of several ear equalization techniques
• To equalize his air spaces on ascent a diver releases air from his body air spaces so that they do not become overfull by
- breathing normally, this releases extra air from his lungs every time he exhales
- ascending slowly and allowing the extra air in his ears, sinuses and mask to bubble out on its own
2. Buoyancy
Divers control their buoyancy (whether they sink, float up, or remain “neutrally buoyant” without floating or sinking) by adjusting their lung volume and buoyancy compensator (BCD).
As a diver descends, the increased pressure causes the air in his BCD and wetsuit (there are small bubble trapped in neoprene) to compress. He becomes negatively buoyant (sinks). As he sinks, the air in his dive gear compresses more and he sinks more quickly. If he does not add air to his BCD to compensate for his increasingly negative buoyancy, a diver can quickly find himself fighting an uncontrolled descent.
In the opposite scenario, as a diver ascends, the air in his BCD and wetsuit expands. The expanding air makes the diver positively buoyant, and he begins to float up. As he floats towards the surface, the ambient pressure decreases and the air in his dive gear continues to expand. A diver must continuously vent air from his BCD during ascent or he risks an uncontrolled, rapid ascent (one of the most dangerous things a diver can do).
A diver must add air to his BCD as he descends and release air from his BCD as he ascends. This may seem counterintuitive until a diver understands how pressure changes effect buoyancy.
3. Bottom Times
Bottom time refers to the amount of time a diver can stay underwater before beginning his ascent. Ambient pressure effects bottom time in two important ways.
• Increased Air Consumption Reduces Bottom Times
The air that a diver breathes is compressed by the surrounding pressure. If a diver descends to 33 feet, or 2 ATA of pressure, the air he breathes is compressed to half of its original volume. Each time the diver inhales, it takes twice as much air to fill his lungs than it does at the surface. This diver will breath use his air up twice as quickly (or in half the time in half the time) as he would at the surface. A diver will use up his available air more quickly the deeper he goes.
• Increased Nitrogen Absorption Reduces Bottom Times
The greater the ambient pressure, the more rapidly a diver's body tissues will absorb nitrogen. Without getting into specifics, a diver can only allow his tissues a certain amount of nitrogen absorption before he begins his ascent, or he runs an unacceptable risk of decompression illness without mandatory decompression stops. The deeper a diver goes, the less time he has before his tissues absorb the maximum allowable amount of nitrogen.
Because pressure becomes greater with depth, both air consumption rates and nitrogen absorption increase the deeper a diver goes. One of these two factors will limit a diver's bottom time.
4. Rapid Pressure Changes Can Cause Decompression Sickness (the Bends)
Increased pressure underwater causes a diver's body tissues to absorb more nitrogen gas than they would normally contain at the surface. If a diver ascends slowly, this nitrogen gas expands bit by bit and the excess nitrogen is safely metabolized and released.
However, the body can only metabolize nitrogen so quickly. The faster a diver ascends, the faster nitrogen expands and must be removed from his tissues. If a diver goes through too great of pressure change too quickly, his body can not metabolize all of the expanding nitrogen and the excess nitrogen forms bubbles in his tissues and blood.
These nitrogen bubbles can cause decompression sickness (DCS) by blocking blood flow to various parts of the body, causing strokes, paralysis, and other life threatening problems. Rapid pressure changes are one of the most common causes of DCS.
The Greatest Pressure Changes Are Closest to the Surface.
The closer a diver is to the surface, the more rapidly the pressure changes.
Depth Change / Pressure Change / Pressure Increase
66 to 99 feet / 3 ATA to 4 ATA / x 1.33
33 to 66 feet / 2 ATA to 3 ATA / x 1.5
0 to 33 feet / 1 ATA to 2 ATA / x 2.0
Look at what happens really close to the surface:
10 to 15 feet / 1.30 ATA to 1.45 ATA / x 1.12
5 to 10 feet / 1.15 ATA to 1.30 ATA / x 1.13
0 to 5 feet / 1.00 ATA to 1.15 ATA / x 1.15
A diver must compensate for the changing pressure more frequently the closer he is to the surface. The more shallow his depth:
• the more frequently a diver must manually equalize his ears and mask.
• the more frequently a diver must adjust his buoyancy to avoid uncontrolled ascents and descents
Divers must take special care during the last portion of the ascent. Never, never, shoot straight to the surface after a safety stop. The last 15 feet are the greatest pressure change and need to be taken more slowly than the rest of the ascent.
Most beginner dives are conducted in the first 40 feet of water for safety purposes and to minimize nitrogen absorption and the risk of DCS. This is as it should be. However, keep in mind that it is more difficult for a diver to control his buoyancy and equalize and in shallow water than in deeper water because the pressure changes are more extreme!
Source: http://scuba.about.com/od/scuba101/a/Under-Pressure.htm
11.12.2010 - Learn to Scuba Dive Everything You Need to Know About Learning to Scuba Dive
If you've just decided to learn to dive you've made an excellent decision and if you're not quite sure yet, let me help you make an excellent decision. Let's have a look at everything you need to know about learning to dive.
What courses are available?
Introductory courses can be as brief as a half day trial in a swimming pool all the way through to full certification. Courses may have slightly different names but they are generally versions of the below courses:
Discover Scuba Diving A brief half day or more introduction to diving. This course provides a first experience of scuba diving under the watchful eye of a scuba professional.
Scuba Diver The Scuba Diver course is an abbreviated Open Water Course that is commonly taken by people who either don't have enough time do a full Open Water Course or who don't need a certification for the type of diving that they enjoy.
Open Water Diver The Open Water course is the most common course and a full introduction to scuba diving. The course takes 3 days or more and once you complete it you'll be certified for life and ready to go on to further training and a lifetime of great diving.
Where should I learn?
You can learn to dive almost anywhere in the world, so this will usually depend on where you live and where you spend your vacations.
When deciding which dive center to learn at it's important to understand the differences between certification agencies and even more important to feel comfortable with your instructor.
How fit and healthy do I need to be?
You don't need to be an Olympic athlete, but you will need to be in good overall health. There are some conditions that may prevent you from diving and you'll need to pass some basic water skills test, so if you're generally healthy and can swim and float well enough you should be ok.
What equipment to I need?
You won't usually need any equipment when you start to dive as it can all be rented for the duration of the course, but some dive centers may prefer you to buy your own mask, snorkel, and fins. Once you're certified there are all sorts of things to buy and many divers love new dive gadgets just as much as the actual diving.
What will I learn?
If you do a Discover Scuba Diving course you'll learn the basics of dive safety and a few basic skills to make sure you're safe underwater. During the Open Water course you'll learn all of the basic skills that you'll need to be able to dive accompanied by a buddy who is also Open Water certified without the supervision of a dive professional. Here are some of the basic skills you'll learn in an Open Water course:
Open Water Skills Overview
What's next?
Once you've completed the Open Water Course and you're a certified diver you may like to do further courses like Advanced Open Water and Rescue Diver or even go on to become a professional Divemaster, Instructor, Technical Diver, Commercial Diver, or even Military Diver. There are also many diving specialty courses that you can study that will broaden and enhance your underwater experiences.
Source: http://scuba.about.com/od/learntodive/a/learntodive.htm
10.12.2010 - 3 Pieces of Gear Every Diver (and Student Diver) Should Have Owning Your Gear Makes Diving, and Dive Training, Easier
Scuba gear is expensive. With the high baggage fees most airlines charge to carry scuba gear, it is not always practical for recreational and casual divers to own an entire set of gear. A full set of scuba gear usually includes expensive, heavy items such as a buoyancy compensator, regulator and wetsuit. However, for a few hundred dollars or less, certified and student divers can assemble a basic set of personal gear which will increase their comfort during both training and recreational diving. Here are three pieces of scuba gear that every diver should own.
Image reproduced with the permission of Cressi.
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Image reproduced with the permission of Oceanic.
Fins come in many different styles. Changing a diver's fins may completely change how he swims. Divers become accustomed to the level of resistance and feel of a certain pair of fins. Consequently, using the same set of fins on every dive usually improves a diver's skills because he learns to use that particular pair of fins correctly. This is also true for student divers, who may benefit by learning to dive in the same set of fins they plan to use once certified. Remember that on vacation, styles such as split fins or fins that accommodate booties may not be available to rent at a dive shop
Learn about different fins styles before making a purchase.
Image reproduced with the permission of Oceanic.
Snorkels are recommended safety gear, but divers also use them to explore the underwater world without a tank. Snorkeling can be a great way to get in some extra underwater time between or after dives.
Snorkels available to rent do not always come with the features divers prefer. Rental snorkels, in general, are simple plastic tubes without dry or semi-dry tops or purge valves. Many dive shops provide disposable, low-quality snorkels with their rental gear simply because divers and snorkelers tend to loose them.
Source:
http://scuba.about.com/od/equipment/tp/3PiecesOfGearForEveryDiver.htm
09.12.2010 - Under Pressure The Basic Consequences of Depth and Pressure in Scuba Diving
How does pressure change underwater and how do pressure changes effect aspects of scuba diving such as equalization, buoyancy, bottom time, and the risk of decompression sickness? Review the fundamentals of pressure and scuba diving, and discover a concept no one told me during my open water course: that pressure changes more rapidly the closer a diver is to the surface.
The Basics
• Air Has Weight
Yes, air actually has weight. The weight of air experts pressure on your body - about 14.7 psi (pounds per a square inch). This amount of pressure is called one atmosphere of pressure because it is the amount of pressure the earth's atmosphere exerts. Most pressure measurements in scuba diving are given in units of atmospheres or ATA.
• Pressure Increases With Depth
The weight of the water above a diver exerts pressure on his body. The deeper a diver descends, the more water he has above him, and the more pressure it exerts on his body. The pressure a diver experiences at a certain depth is the sum of all the pressures above him, both from the water and the air.
• every 33 feet of salt water = 1 ATA of pressure
• pressure a diver experiences = water pressure + 1 ATA (from the atmosphere)
Total Pressure at Standard Depths*
Depth / Atmospheric Pressure + Water Pressure / Total Pressure
0 feet / 1 ATA + 0 ATA / 1 ATA
15 feet / 1 ATA + 0.45 ATA / 1 .45 ATA
33 feet / 1 ATA + 1 ATA / 2 ATA
40 feet / 1 ATA + 1.21 ATA / 2.2 ATA
66 feet / 1 ATA + 2 ATA / 3 ATA
99 feet / 1 ATA + 3 ATA / 4 ATA
*this is only for salt water at sea level
• Water Pressure Compresses Air
Air in a diver's body air spaces and dive gear will compress as pressure increases (and expand as pressure decreases). Air compresses according to Boyle's Law.
• Boyle's Law: Air Volume = 1/ Pressure
Not a math person? This means that the deeper you go, the more air compresses. To find out how much, make a fraction of 1 over the pressure. If the pressure is 2 ATA, then the volume of the compressed air is ½ of its original size at the surface.
Pressure Effects Many Aspects of Diving
Now that you understand the basics, let's look at how pressure effects four basic aspects of diving.
1. Equalization
As a diver descends, the pressure increase causes the air in his body's air spaces to compress. The air spaces in his ears, mask, and lungs become like vacuums as the compressing air creates a negative pressure. Delicate membranes, like the ear drum, to be sucked into theses air spaces causing pain and injury.
On ascent, the reverse happens. Decreasing pressure causes the air in a diver's air spaces to expand. The air spaces in his ears and lungs experience a positive pressure as they become overfull of air. In a worst case scenario this could burst a diver's lungs or eardrums! This the reason that a diver should never hold his breath underwater - if he holds his breath and ascends even a tiny bit, he could over-expand his lungs.
To avoid a pressure related injury (such as an ear barotrauma) a diver must equalize the pressure in his body's air spaces with the pressure around him.
• To equalize his air spaces on descent a diver adds air to his body airspaces to counteract the "vacuum" effect by
- breathing normally, this adds air to his lungs every time he inhales
- adding air to his mask by breathing out his nose
- adding air to his ears and sinuses by using one of several ear equalization techniques
• To equalize his air spaces on ascent a diver releases air from his body air spaces so that they do not become overfull by
- breathing normally, this releases extra air from his lungs every time he exhales
- ascending slowly and allowing the extra air in his ears, sinuses and mask to bubble out on its own
2. Buoyancy
Divers control their buoyancy (whether they sink, float up, or remain “neutrally buoyant” without floating or sinking) by adjusting their lung volume and buoyancy compensator (BCD).
As a diver descends, the increased pressure causes the air in his BCD and wetsuit (there are small bubble trapped in neoprene) to compress. He becomes negatively buoyant (sinks). As he sinks, the air in his dive gear compresses more and he sinks more quickly. If he does not add air to his BCD to compensate for his increasingly negative buoyancy, a diver can quickly find himself fighting an uncontrolled descent.
In the opposite scenario, as a diver ascends, the air in his BCD and wetsuit expands. The expanding air makes the diver positively buoyant, and he begins to float up. As he floats towards the surface, the ambient pressure decreases and the air in his dive gear continues to expand. A diver must continuously vent air from his BCD during ascent or he risks an uncontrolled, rapid ascent (one of the most dangerous things a diver can do).
A diver must add air to his BCD as he descends and release air from his BCD as he ascends. This may seem counterintuitive until a diver understands how pressure changes effect buoyancy.
3. Bottom Times
Bottom time refers to the amount of time a diver can stay underwater before beginning his ascent. Ambient pressure effects bottom time in two important ways.
• Increased Air Consumption Reduces Bottom Times
The air that a diver breathes is compressed by the surrounding pressure. If a diver descends to 33 feet, or 2 ATA of pressure, the air he breathes is compressed to half of its original volume. Each time the diver inhales, it takes twice as much air to fill his lungs than it does at the surface. This diver will breath use his air up twice as quickly (or in half the time in half the time) as he would at the surface. A diver will use up his available air more quickly the deeper he goes.
• Increased Nitrogen Absorption Reduces Bottom Times
The greater the ambient pressure, the more rapidly a diver's body tissues will absorb nitrogen. Without getting into specifics, a diver can only allow his tissues a certain amount of nitrogen absorption before he begins his ascent, or he runs an unacceptable risk of decompression illness without mandatory decompression stops. The deeper a diver goes, the less time he has before his tissues absorb the maximum allowable amount of nitrogen.
Because pressure becomes greater with depth, both air consumption rates and nitrogen absorption increase the deeper a diver goes. One of these two factors will limit a diver's bottom time.
4. Rapid Pressure Changes Can Cause Decompression Sickness (the Bends)
Increased pressure underwater causes a diver's body tissues to absorb more nitrogen gas than they would normally contain at the surface. If a diver ascends slowly, this nitrogen gas expands bit by bit and the excess nitrogen is safely metabolized and released.
However, the body can only metabolize nitrogen so quickly. The faster a diver ascends, the faster nitrogen expands and must be removed from his tissues. If a diver goes through too great of pressure change too quickly, his body can not metabolize all of the expanding nitrogen and the excess nitrogen forms bubbles in his tissues and blood.
These nitrogen bubbles can cause decompression sickness (DCS) by blocking blood flow to various parts of the body, causing strokes, paralysis, and other life threatening problems. Rapid pressure changes are one of the most common causes of DCS.
The Greatest Pressure Changes Are Closest to the Surface.
The closer a diver is to the surface, the more rapidly the pressure changes.
Depth Change / Pressure Change / Pressure Increase
66 to 99 feet / 3 ATA to 4 ATA / x 1.33
33 to 66 feet / 2 ATA to 3 ATA / x 1.5
0 to 33 feet / 1 ATA to 2 ATA / x 2.0
Look at what happens really close to the surface:
10 to 15 feet / 1.30 ATA to 1.45 ATA / x 1.12
5 to 10 feet / 1.15 ATA to 1.30 ATA / x 1.13
0 to 5 feet / 1.00 ATA to 1.15 ATA / x 1.15
A diver must compensate for the changing pressure more frequently the closer he is to the surface. The more shallow his depth:
• the more frequently a diver must manually equalize his ears and mask.
• the more frequently a diver must adjust his buoyancy to avoid uncontrolled ascents and descents
Divers must take special care during the last portion of the ascent. Never, never, shoot straight to the surface after a safety stop. The last 15 feet are the greatest pressure change and need to be taken more slowly than the rest of the ascent.
Most beginner dives are conducted in the first 40 feet of water for safety purposes and to minimize nitrogen absorption and the risk of DCS. This is as it should be. However, keep in mind that it is more difficult for a diver to control his buoyancy and equalize and in shallow water than in deeper water because the pressure changes are more extreme!
Source: http://scuba.about.com/od/scuba101/a/Under-Pressure.htm
08.12.2010 - Learn to Scuba Dive Everything You Need to Know About Learning to Scuba Dive
If you've just decided to learn to dive you've made an excellent decision and if you're not quite sure yet, let me help you make an excellent decision. Let's have a look at everything you need to know about learning to dive.
What courses are available?
Introductory courses can be as brief as a half day trial in a swimming pool all the way through to full certification. Courses may have slightly different names but they are generally versions of the below courses:
Discover Scuba Diving A brief half day or more introduction to diving. This course provides a first experience of scuba diving under the watchful eye of a scuba professional.
Scuba Diver The Scuba Diver course is an abbreviated Open Water Course that is commonly taken by people who either don't have enough time do a full Open Water Course or who don't need a certification for the type of diving that they enjoy.
Open Water Diver The Open Water course is the most common course and a full introduction to scuba diving. The course takes 3 days or more and once you complete it you'll be certified for life and ready to go on to further training and a lifetime of great diving.
Where should I learn?
You can learn to dive almost anywhere in the world, so this will usually depend on where you live and where you spend your vacations.
When deciding which dive center to learn at it's important to understand the differences between certification agencies and even more important to feel comfortable with your instructor.
How fit and healthy do I need to be?
You don't need to be an Olympic athlete, but you will need to be in good overall health. There are some conditions that may prevent you from diving and you'll need to pass some basic water skills test, so if you're generally healthy and can swim and float well enough you should be ok.
What equipment to I need?
You won't usually need any equipment when you start to dive as it can all be rented for the duration of the course, but some dive centers may prefer you to buy your own mask, snorkel, and fins. Once you're certified there are all sorts of things to buy and many divers love new dive gadgets just as much as the actual diving.
What will I learn?
If you do a Discover Scuba Diving course you'll learn the basics of dive safety and a few basic skills to make sure you're safe underwater. During the Open Water course you'll learn all of the basic skills that you'll need to be able to dive accompanied by a buddy who is also Open Water certified without the supervision of a dive professional. Here are some of the basic skills you'll learn in an Open Water course:
Open Water Skills Overview
What's next?
Once you've completed the Open Water Course and you're a certified diver you may like to do further courses like Advanced Open Water and Rescue Diver or even go on to become a professional Divemaster, Instructor, Technical Diver, Commercial Diver, or even Military Diver. There are also many diving specialty courses that you can study that will broaden and enhance your underwater experiences.
Source: http://scuba.about.com/od/learntodive/a/learntodive.htm
07.12.2010 - All About Decompression Sickness
Causes, Types, and Symptoms
Also known as The Bends and Caisson Disease, Decompression Sickness is an illness that can affect divers or other people (such as miners) who are in a situation that involves pressure rapidly decreasing around the body.
DCS, as it is commonly know, is caused by a build up of nitrogen bubbles in the body. When we breathe, approximately 79 of the air we're breathing is nitrogen. As we descend in water, the pressure around our bodies increases, causing nitrogen to be absorbed into our body tissues. This is not actually harmful and it's quite possible for the body to continue to absorb nitrogen until it reaches a point called saturation, which is the point at which the pressure in the tissues equals the surrounding pressure.
The problem arises when this pressure needs to be released. In order to release the nitrogen slowly from the body, a diver must ascend slowly and carry out decompression stops if necessary - this allows the nitrogen to slowly seep out of the body tissues and either immediately revert to being a gas or to become tiny harmless bubbles which will eventually become revert to gas. This process is called "Off-gassing" and is normally carried out through the lungs.
If a diver ascends too fast and the nitrogen escapes the body tissue too quickly it becomes bubbles in the body and this leads to Decompression Sickness. The bubbles must normally be on the arterial side of the circulatory system to be harmful - they are usually harmless on the venous side. There are several types of Decompression Sickness:
Type I Decompression Sickness
Type I Decompression Sickness is the least serious form of Decompression Sickness. It normally involves only pain in the body and is not immediately life threatening. It is important to note that symptoms of Type I Decompression Sickness may be warning signs of more serious problems.
- Cutaneous Decompression Sickness
This is when the nitrogen bubbles come out of solution in skin capillaries. This normally results in a red rash, often on the shoulders and chest.
- Joint and Limb Pain Decompression Sickness
This type is characterized by aching in the joints. It is not known exactly what causes the pain as bubbles in the joint would not have this effect. The common theory is that it is caused by the bubbles aggravating bone marrow, tendons, and joints. The pain can be in one place or it can move around the joint. It is unusual for bisymmetrical symptoms to occur.
Type II Decompression Sickness
Type II Decompression Sickness is the most serious and can be immediately life-threatening. The main effect is on the nervous system.
- Neurological Decompression Sickness
When nitrogen bubbles affect the nervous system they can cause problems throughout the body. This type of Decompression Sickness normally shows as tingling, numbness, respiratory problems, and unconsciousness. Symptoms can spread quickly and if left untreated can lead to paralysis or even death.
- Pulmonary Decompression Sickness
This is a rare form of Decompression Sickness that occurs when bubbles form in lung capillaries. Fortunately, the majority of the time bubbles dissolve naturally through the lungs. However, it is possible for them to interrupt blood flow to the lungs which can lead to serious and life-threatening respiratory and heart problems.
- Cerebral Decompression Sickness
It is possible for bubbles that make their way into the arterial blood stream to move to the brain and to cause an arterial gas embolism. This is extremely dangerous and can be identified by symptoms such as blurred vision, headaches, confusion, and unconsciousness.
Other Forms of Decompression Sickness
Extreme tiredness is very common in cases of Decompression Sickness and can sometimes be the only symptom of Decompression Sickness present. It is not know what causes this but you should be aware that extreme fatigue could be a sign of more serious problems. It is also possible for Decompression Sickness to occur in the inner-ear. This is caused by bubbles forming in the cochlea's perilymph during decompression. The result can be hearing loss, dizziness, ringing of the ears, and vertigo.
Symptoms
Decompression Sickness can manifest itself in many different ways and has many different symptoms, but the most common symptoms are:
- Extreme Fatigue
- Joint and Limb Pain
- Tingling
- Numbness
- Red Rash on Skin
- Respiratory Problems
- Heart Problems
- Dizziness
- Blurred Vision
- Headaches
- Confusion
- Unconsciousness
- Ringing of the Ears
- Vertigo
- Stomach Sickness
Risk Factors
Every diver has a different level of risk of Decompression Sickness. Many risk factors are still not fully understood, but there are a few basic factors that doctors agree increase the chance of developing Decompression Sickness:
- Bodyfat
The theory is that nitrogen absorbs more easily into fat, so an overweight diver is at a greater risk of decompression sickness.
- Exercise
Interestingly, exercise has both a positive and negative effect. Exercise at least 12 hours before a dive seems to produce proteins that protect the body and decrease the risk of Decompression Sickness. On the other hand, exercise less than 12 hours before a dive can raise the number of gas micronuclei on which bubbles form and this increases the risk of Decompression Sickness. Exercise immediately after a dive increases the risk of bubbles forming as blood pressure is increased and bubbles can more easily be transferred from the venous to the arterial side of the circulatory system.
- Gender
Theoretically women should have a higher risk of Decompression Sickness due to the fact that women typically have a higher bodyfat content. However, this has not been proven in studies and it's possible that gender does not affect the chances of suffering from Decompression Sickness.
- Age
Generally, older people are at an increased risk of Decompression Sickness. This is due to less efficient circulatory and respiratory systems.
- Fitness
Fitness definitely decreases the risk of Decompression Sickness. A fitter body is able to tolerate more physical stress, including Decompression Sickness.
- Dehydration
Dehydration causes less blood to be available for gas exchange which makes it more difficult for the body to off-gas, increasing the risk of Decompression Sickness.
- Injury and Illness
Injury and illness can affect normal circulation, increasing the risk of Decompression Sickness.
- Alcohol
Consuming alcohol before or after a dive accelerates circulation which helps tissues to load with gas. Alcohol also dilates capillaries which can increase the rate of nitrogen released.
- Carbon Dioxide
Improper breathing can lead to elevated levels of carbon dioxide which interferes with the bodies ability to transport gas. This will lead to an increased chance of Decompression Sickness.
- Cold
It is generally believed by doctors that diving in cold water increases the risk of Decompression Sickness. This is due to the body working harder to keep warm as it becomes colder. Meaning that when the body is warmer it is able to absorb gas normally but as it becomes cold it has difficult offing the gas.
- Altitude and Flying After Diving
When ascending on land or in a plane, the atmospheric pressure changes and this increases the chances of Decompression Sickness. It is best not to ascend above 300 meters (1000 feet) or fly after diving. Consult the current flying after diving guidelines to know when it is safe to fly.
- Patent Foramen Ovale (PFO) - Hole in the Heart
As a fetus, a baby doesn't breathe and needs a way for blood to bypass the lungs until it is born. The body achieves this by having a small opening in the middle of the heart that allows blood to bypass the lungs. Normally, this hole would close within a year of birth, but in approximately 20-34 of people this does not happen, leaving a permanent opening in the heart. Usually, a flap grows over the opening and there is no effect. However, in some cases the flap allows blood to pass through the opening. This means that bubbles are more easily able to pass from the venous to the arterial side of the circulatory system, greatly increasing the risk of Decompression Sickness. It has been found that a large proportion of divers who suffered from Decompression Sickness had a PFO.
- Reverse Profiles
The jury is still out on reverse profiling, or making a deeper dive after a shallower dive. Theoretically it should increase the risk of Decompression Sickness, but this has not been proven scientifically. It would still be better to err on the side of caution.
Prevention
As there are many risk factors, there are also many methods of prevention. Here's a basic checklist that will help you lower your risk of suffering from Decompression Sickness:
- Always ascend slowly and safely from every dive
- Don't push your limits and do all required decompression stops
- Keep physically fit and within a healthy weight range
- Don't exercise within 12 hours of diving
- Don't ascend to altitude or fly immediately after diving
- Breathe normally throughout the dive, don't exert yourself or skip breathe
- Make sure you're adequately hydrated before every dive
- Don't drink alcohol before or after diving and never dive when hungover
- Get checked out by a doctor to find out if you have a PFO
- Avoid reverse profiling - just in case
Treatment
Immediate on the scene treatment consists of oxygen therapy and basic first aid. This should be followed as quickly as possible by recompression treatment in a recompression chamber. When treating Decompression Sickness the delay in beginning recompression treatment can be the biggest single cause of residual effects.
Source:
http://scuba.about.com/od/divemedicinesafety/a/dcs.htm
05.12.2010 - How to Clear a Scuba Mask of Water
I was kneeling on a shallow water platform during my open water course when my diving instructor floated up to me and signaled me to put a little water in my scuba mask. Forgetting the predive briefing, I glared at him in annoyance. My mask was fine. Why would I want to let water in to a perfectly sealed, water tight scuba mask?
Although it may be counterintuitive to purposefully let water into a well-sealed mask, the mask clearing skill is one of the most important skills of the open water course. Leaky masks are not fun, but every scuba diver will find water in his mask at some point in his diving career (usually sooner rather than later). He will need to be able to efficiently get the water out without surfacing and without panicking. With a little practice, mask clearing becomes easy and automatic. Here's how to clear your mask of water.
If this is the first time you have tried to clear a mask of water, take a moment to relax, slow your breathing rate, and review the steps of mask clearing in your mind. It is normal to be nervous about clearing your mask for the first time, but if you work through the skill step by step you should have no problems. You can even do a “dry run” by practicing the steps of mask clearing without adding any water to the mask until you are confident. When you are calm and ready to begin the skill, signal to your instructor that you are “okay” and about to begin.
Before you can practice clearing water from your mask, you need to let some water into it. Allow a small amount of water to trickle into the mask in a controlled manner. It is no fun to suddenly find yourself with a completely flooded mask!
The instructor in the photo demonstrates one method of controlling the flow of water as it enters the mask. She pinches the upper mask skirt, letting just a tiny amount of water to trickle in. This method of adding water to the mask works well because it exposes divers to the sensation of water flowing over or near their eyes; something that may happen on a dive.
An alternate method of putting water in the mask is to gently lift the bottom of the mask away from your face. Water will slowly enter the mask because it has to displace the air already in the mask. This method does not allow as much control of the flow of water entering the mask.
Do you wear contact lenses or have very sensitive eyes? Don't worry, it is perfectly fine to close your eyes during this skill.
If this is your first time practicing clearing your mask, fill it to just below eye level. Take a moment to relax and get used to the sensation of water in the mask. Practice breathing in and out using your mouth only, or breathe in your mouth and out your nose. If you feel water entering your nostrils, breathe out your nose, tilt your head down, and look at the floor. This traps air bubbles in your nose and prevents water from flowing in. See, there is nothing scary about it!
Start by holding the top of the mask frame firmly against your forehead. You can do this with one hand placed in the center of the mask frame, or a finger on each upper edge. When you are ready, look down to keep water out of your nose and take a deep breath from the regulator. Begin exhaling slowly but forcefully through your nose, then tilt your head up while continuing to exhale. If you have difficulty exhaling from your nose, it helps to imagine that you have some extra sticky, nasty boogers up your nostrils that you need to blow out. Focus on your imaginary boogers and blooooow.
Your exhalation should last at least a few seconds. As a goal, try to breathe out your nose for a minimum of five seconds. Air from your nose bubbles upwards and fills the mask, forcing the water out the bottom. It is important to maintain firm pressure on the upper frame of the mask, or the exhaled air will simply escape from the top of the mask. Remember to look upwards while exhaling, otherwise the air will just flow out the bottom and sides of the mask.
Before you finish exhaling, look back down towards the floor. By doing this any water remaining in the mask will not flow up into your nose.
On a first attempt, you may not be able to completely clear a mask of water with only one breath. Don't worry. If water remains in the mask, look down at the floor and take a few moments to catch your breath. Repeat the exhalation step, focusing on breathing out your nose slowly, holding the mask firmly against your forehead, and looking up. It may take a few iterations to get the last few drops of water out, and that's okay.
If you wear contacts or have sensitive eyes, you may still have your eyes closed during this stage. Once you think you have cleared the water out of the mask, open your eyes slowly. Your instructor may tap you gently to let you know the skill is finished. It is normal to feel that your face is still wet – it is! You just had water in your mask and you haven't had a chance to let it dry yet. Don't worry, any water on your face will dry in a few moments.
Good job! Now you know how to clear your mask of water. Practice this skill until it becomes automatic and comfortable. Once you are an expert at mask clearing, try the exercise in a variety of positions. You can even clear your mask while maintaining a proper, horizontal swimming position.
This skill has another application. If a mask fogs up during a dive (click here to learn more about foggy masks), you can clear the fog from the mask lens using the mask clearing skill. Simply allow a small amount of water to drip into the mask, then tilt your head down so that the water flows down into the mask lens. Shake you head gently side to side so that the water contacts all parts of the mask lens, then clear the mask normally. Presto! Now you can enjoy a clear view of the underwater world during every part of the dive.
Source: http://scuba.about.com/od/skills/ss/How-To-Clear-A-Scuba-Mask-Of-Water.htm
01.12.2010 - The Pre-Dive Safety Check for Scuba Diving
Do you consider flying dangerous? Most people will agree that while there are certain risks associated with flying, traveling by plane is fairly safe. One of the reasons that air travel has a fantastic safety record is that pilots complete a long checklist to make sure that a plane is working properly before it ever leaves the ground. Scuba divers have a similar checklist, the pre-dive safety check (or buddy check), to review their scuba gear before hopping into the water. Thankfully, scuba equipment is much less complicated than an airplane, and once a diver becomes comfortable using the pre-dive safety check, reviewing scuba gear before a dive takes only a matter of seconds.
Source: http://scuba.about.com/od/skills/ss/The-Pre-Dive-Safety-Check-For-Scuba-Diving.htm
30.11.2010 - About Scuba Diving All the basics you need to know about scuba diving
Scuba diving is swimming underwater using SCUBA - Self Contained Underwater Breathing Apparatus. Using a cylinder of compressed gas to breathe (usually air, but sometimes other gases), scuba divers can stay underwater much longer than would be possible by just holding their breath - for hours or even days!
With the assistance of equipment such as scuba masks, breathing regulators, buoyancy devices, fins, and gauges scuba divers can explore the underwater world. Modern scuba diving is very safe and easy to learn. All basic skills can be learned in as little as three days.
Scuba diving is a sport that is practiced recreationally all around the world and can even be a profession. There are many diving jobs such as recreational divemaster and instructor, commercial diver, police diver, scientific diver, and military diver.
Why do people scuba dive?
For some it's the beauty of the reef and the marine life that inhabits it, for others it's the thrill of discovery deep inside a wreck or cave - everyone has a different reason for scuba diving, but most would agree that it's for the sheer enjoyment of experiencing the underwater world, a world so far removed from ours that it will truly amaze you. Whether you want to relax while photographing brightly colored tropical fish, be thrilled by the power and grace of a school of sharks, or make a living working underwater, scuba diving has it all.
Who can scuba dive?
The simple answer is - almost anyone. Scuba divers are aged from 8 years and over and come from all walks of life. Here are some basic considerations:
- Age
Children as young at 8 years old can start diving with programs taught in the safety of shallow water and aimed specifically at young children. From the age of 10 years old children can be certified as Junior Open Water Divers and those 15 years and older can be certified as Open Water Divers. There are no upper age limits.
- Health
You need to be in a state of good health. This doesn't mean you need to be super-fit, but you have to be free of any serious medical problems. You'll answer a medical questionnaire when you sign up for a course and if you or your instructor have any concerns you will be referred to a medical doctor for assessment. You will also need to be able to swim and float or tread water.
- Disabilities
Scuba diving is accessible to people with physical disabilities. Many instructors are trained to provide courses tailored to physically challenged divers and there are diving societies whose primary goal is to facilitate and promote diving for physically challenged people.
What types of scuba diving are there?
There are many types of scuba diving which means there's always something new to do and see. Here are the most popular types:
- Recreational
Most divers are recreational divers and this is the form of diving that is devoted to having fun. Some divers love looking at fish and coral, but there are also many specialized areas of scuba diving. After Open Water certification you can complete courses in all sorts of specialties including, but not limited to: night diving, wreck diving, deep diving, navigation, fish identification, underwater naturalism, photography, videography, cave diving, ice diving, altitude diving, and rescue diving.
- Technical
Some recreational divers want to explore the marine world even further than recreational diving equipment and training allows. Technical diving encompasses areas such as extreme deep diving, advanced wreck diving, and advanced cave diving. Technical diving is for very experienced recreational divers and requires specialised training and equipment.
- Commercial
Commercial divers scuba dive for a living. They build underwater structures such as oil platforms, carry out underwater maintenance, conduct surveys, create maps, participate in salvage operations, and work in many other diving related occupations.
- Military
Military diving is similar to commercial diving but also involves such tasks as underwater surveillance, mine clearing, and military research. Military divers and scientists have historically been responsible for most advances in dive equipment and dive medicine.
Where do people scuba dive?
You can scuba dive anywhere you can find water. Over two-thirds of the planet is covered by water, so you can dive almost anywhere. Tropical coral reefs tend to be most popular amongst recreational divers but there are also many wonderful things to be found in cold water environments such as lakes, rivers, and quarries.
Divers can be found in all corners of the globe from the tropical reefs of the Caribbean and the Great Barrier Reef, to the world's biggest lake in Siberia - even under the ice of Antarctica. While most dive shops and resorts operate in warm tropical environments it's also common to find local dive centers and dive clubs in most cities around the world - even inland cities with no water.
Source: http://scuba.about.com/od/whatisscubadiving/a/About_Scuba.htm
29.11.2010 - Sand Tiger Shark (Carcharias taurus)
Common Name: Sand Tiger Shark
Scientific Name: Carcharias taurus
Also Known As: Grey Nurse Shark, Spotted Ragged-Tooth Shark
Description: Pale gray in color with a white underside, Sand Tiger Sharks have a stout body and a short pointed snout. With sharp ragged, and protruding teeth, the Sand Tiger has a dangerous appearance that is deceptive, as this is a placid, and often even timid, Shark.
Classification:
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Lamniformes
Family: Odontaspididae
Genus: Carcharias
Maximum Size: 320cm
Habitat & Range: Sand Tiger Sharks are found in all warm water seas except for the eastern Pacific Ocean. They inhabit coastal reef areas and can be found anywhere from 0-400 feet. They are often found in rocky coastal areas in cool to warm water.
Diet: Sand Tiger Sharks eat a variety of small bony fish, along with other small sharks, skates, and rays..
Lifespan: 15 or more years in the wild.
Predators: Juveniles can be at risk from other sharks. Adults have no predators in the sea.
Red List Status: Vulnerable
Source: http://scuba.about.com/od/sharks/a/sandtigershark.htm
28.11.2010 - Open Water Certification Your Questions Answered
If you're thinking about learning to dive or you want to know a bit more about what to expect in your certification course I've answered the most common questions here.
What is the Open Water course?
The Open Water course is the basic scuba diving certification course taught by all certification agencies. There are small differences in course content between agencies, but they all cover the same basic skills and knowledge you will need to know as an independent diver.
Who can enroll?
Children as young as 10 years old (12 years old in some countries) can enroll in the Junior Open Water course and those 15 years and older can enroll in the Open Water course. Junior Open Water certified divers are automatically upgraded to Open Water divers on their 15th birthday with no need for recertification.
You'll also need to be in good health with no major health problems.
What does the course qualify you to do?
When you're certified as an Open Water diver you'll be able to dive to 60 feet / 18 meters (40 feet / 12 meters for 10-12 year olds) whenever you're accompanied by a fellow of the same or higher certification level (the other diver must be 18 or older for Junior Open Water divers). You don't have to be accompanied by a Divemaster or Instructor, but can be if you'd prefer. You're also eligible to do the Advanced Open Water course and many specialties.
How long does the course take?
The course is usually taught over 3 to 5 days in dive vacation destinations, but can also be taught over weeks or even months if taken as a part-time course. The course content is the same but the daily workload is much greater, although still quite manageable, on the shorter course.
What do I have to do to complete the course?
- Knowledge Development
You will be given a text book and videos to watch and will either study independently in your own time, with the assistance of your instructor, or online with guided e-learning. You will learn the basics of diving techniques, how diving affects your body, diving safety, equipment selection and maintenance, dive planning, and preview the skills you'll learn in the water. There will be a test at the end but if you've studied your material you should have no problems passing.
- Confined Water Training
Your confined water training will be conducted in a swimming pool or swimming pool like environment, such as a calm beach. Beginning in water shallow enough to stand up in you'll learn all the basic skills you'll need to confidently and safely enjoy scuba diving. As you gain confidence you'll gradually move into deeper water and learn some more advanced skills and safety drills.
- Open Water Training
This is what it's all about - open water diving. Over four or more dives you'll practice all the skills you've already mastered in confined water out in open water, which means the open ocean or another large body of water that is used for diving. You'll practice the skills with your instructor until you're completely confident and can perform them with ease in a real diving situation. Of course you'll also get to check out everything the underwater world has to offer and hopefully develop a life-long love for diving.
Do I have to renew my certification?
The Open Water certification is forever and never needs to be renewed. However, it is recommended that if you haven't dived for a while (usually a year or more) or feel the need to brush up your skills to do a Scuba Review. This review is a short refresher course with a professional that can be integrated into your first regular dive.
Source: http://scuba.about.com/od/certificationopenwater/a/openwatercert.htm
27.11.2010 - About Scuba Diving All the basics you need to know about scuba diving
Scuba diving is swimming underwater using SCUBA - Self Contained Underwater Breathing Apparatus. Using a cylinder of compressed gas to breathe (usually air, but sometimes other gases), scuba divers can stay underwater much longer than would be possible by just holding their breath - for hours or even days!
With the assistance of equipment such as scuba masks, breathing regulators, buoyancy devices, fins, and gauges scuba divers can explore the underwater world. Modern scuba diving is very safe and easy to learn. All basic skills can be learned in as little as three days.
Scuba diving is a sport that is practiced recreationally all around the world and can even be a profession. There are many diving jobs such as recreational divemaster and instructor, commercial diver, police diver, scientific diver, and military diver.
Why do people scuba dive?
For some it's the beauty of the reef and the marine life that inhabits it, for others it's the thrill of discovery deep inside a wreck or cave - everyone has a different reason for scuba diving, but most would agree that it's for the sheer enjoyment of experiencing the underwater world, a world so far removed from ours that it will truly amaze you. Whether you want to relax while photographing brightly colored tropical fish, be thrilled by the power and grace of a school of sharks, or make a living working underwater, scuba diving has it all.
Who can scuba dive?
The simple answer is - almost anyone. Scuba divers are aged from 8 years and over and come from all walks of life. Here are some basic considerations:
- Age
Children as young at 8 years old can start diving with programs taught in the safety of shallow water and aimed specifically at young children. From the age of 10 years old children can be certified as Junior Open Water Divers and those 15 years and older can be certified as Open Water Divers. There are no upper age limits.
- Health
You need to be in a state of good health. This doesn't mean you need to be super-fit, but you have to be free of any serious medical problems. You'll answer a medical questionnaire when you sign up for a course and if you or your instructor have any concerns you will be referred to a medical doctor for assessment. You will also need to be able to swim and float or tread water.
- Disabilities
Scuba diving is accessible to people with physical disabilities. Many instructors are trained to provide courses tailored to physically challenged divers and there are diving societies whose primary goal is to facilitate and promote diving for physically challenged people.
What types of scuba diving are there?
There are many types of scuba diving which means there's always something new to do and see. Here are the most popular types:
- Recreational
Most divers are recreational divers and this is the form of diving that is devoted to having fun. Some divers love looking at fish and coral, but there are also many specialized areas of scuba diving. After Open Water certification you can complete courses in all sorts of specialties including, but not limited to: night diving, wreck diving, deep diving, navigation, fish identification, underwater naturalism, photography, videography, cave diving, ice diving, altitude diving, and rescue diving.
- Technical
Some recreational divers want to explore the marine world even further than recreational diving equipment and training allows. Technical diving encompasses areas such as extreme deep diving, advanced wreck diving, and advanced cave diving. Technical diving is for very experienced recreational divers and requires specialised training and equipment.
- Commercial
Commercial divers scuba dive for a living. They build underwater structures such as oil platforms, carry out underwater maintenance, conduct surveys, create maps, participate in salvage operations, and work in many other diving related occupations.
- Military
Military diving is similar to commercial diving but also involves such tasks as underwater surveillance, mine clearing, and military research. Military divers and scientists have historically been responsible for most advances in dive equipment and dive medicine.
Where do people scuba dive?
You can scuba dive anywhere you can find water. Over two-thirds of the planet is covered by water, so you can dive almost anywhere. Tropical coral reefs tend to be most popular amongst recreational divers but there are also many wonderful things to be found in cold water environments such as lakes, rivers, and quarries.
Divers can be found in all corners of the globe from the tropical reefs of the Caribbean and the Great Barrier Reef, to the world's biggest lake in Siberia - even under the ice of Antarctica. While most dive shops and resorts operate in warm tropical environments it's also common to find local dive centers and dive clubs in most cities around the world - even inland cities with no water.
Source: http://scuba.about.com/od/whatisscubadiving/a/About_Scuba.htm
26.11.2010 - Open Water Certification Your Questions Answered
If you're thinking about learning to dive or you want to know a bit more about what to expect in your certification course I've answered the most common questions here.
What is the Open Water course?
The Open Water course is the basic scuba diving certification course taught by all certification agencies. There are small differences in course content between agencies, but they all cover the same basic skills and knowledge you will need to know as an independent diver.
Who can enroll?
Children as young as 10 years old (12 years old in some countries) can enroll in the Junior Open Water course and those 15 years and older can enroll in the Open Water course. Junior Open Water certified divers are automatically upgraded to Open Water divers on their 15th birthday with no need for recertification.
You'll also need to be in good health with no major health problems.
What does the course qualify you to do?
When you're certified as an Open Water diver you'll be able to dive to 60 feet / 18 meters (40 feet / 12 meters for 10-12 year olds) whenever you're accompanied by a fellow of the same or higher certification level (the other diver must be 18 or older for Junior Open Water divers). You don't have to be accompanied by a Divemaster or Instructor, but can be if you'd prefer. You're also eligible to do the Advanced Open Water course and many specialties.
How long does the course take?
The course is usually taught over 3 to 5 days in dive vacation destinations, but can also be taught over weeks or even months if taken as a part-time course. The course content is the same but the daily workload is much greater, although still quite manageable, on the shorter course.
What do I have to do to complete the course?
- Knowledge Development
You will be given a text book and videos to watch and will either study independently in your own time, with the assistance of your instructor, or online with guided e-learning. You will learn the basics of diving techniques, how diving affects your body, diving safety, equipment selection and maintenance, dive planning, and preview the skills you'll learn in the water. There will be a test at the end but if you've studied your material you should have no problems passing.
- Confined Water Training
Your confined water training will be conducted in a swimming pool or swimming pool like environment, such as a calm beach. Beginning in water shallow enough to stand up in you'll learn all the basic skills you'll need to confidently and safely enjoy scuba diving. As you gain confidence you'll gradually move into deeper water and learn some more advanced skills and safety drills.
- Open Water Training
This is what it's all about - open water diving. Over four or more dives you'll practice all the skills you've already mastered in confined water out in open water, which means the open ocean or another large body of water that is used for diving. You'll practice the skills with your instructor until you're completely confident and can perform them with ease in a real diving situation. Of course you'll also get to check out everything the underwater world has to offer and hopefully develop a life-long love for diving.
Do I have to renew my certification?
The Open Water certification is forever and never needs to be renewed. However, it is recommended that if you haven't dived for a while (usually a year or more) or feel the need to brush up your skills to do a Scuba Review. This review is a short refresher course with a professional that can be integrated into your first regular dive.
Source: http://scuba.about.com/od/certificationopenwater/a/openwatercert.htm
25.11.2010 - About Scuba Diving, All the basics you need to know about scuba diving
Scuba diving is swimming underwater using SCUBA - Self Contained Underwater Breathing Apparatus. Using a cylinder of compressed gas to breathe (usually air, but sometimes other gases), scuba divers can stay underwater much longer than would be possible by just holding their breath - for hours or even days!
With the assistance of equipment such as scuba masks, breathing regulators, buoyancy devices, fins, and gauges scuba divers can explore the underwater world. Modern scuba diving is very safe and easy to learn. All basic skills can be learned in as little as three days.
Scuba diving is a sport that is practiced recreationally all around the world and can even be a profession. There are many diving jobs such as recreational divemaster and instructor, commercial diver, police diver, scientific diver, and military diver.
Why do people scuba dive?
For some it's the beauty of the reef and the marine life that inhabits it, for others it's the thrill of discovery deep inside a wreck or cave - everyone has a different reason for scuba diving, but most would agree that it's for the sheer enjoyment of experiencing the underwater world, a world so far removed from ours that it will truly amaze you. Whether you want to relax while photographing brightly colored tropical fish, be thrilled by the power and grace of a school of sharks, or make a living working underwater, scuba diving has it all.
Who can scuba dive?
The simple answer is - almost anyone. Scuba divers are aged from 8 years and over and come from all walks of life. Here are some basic considerations:
- Age
Children as young at 8 years old can start diving with programs taught in the safety of shallow water and aimed specifically at young children. From the age of 10 years old children can be certified as Junior Open Water Divers and those 15 years and older can be certified as Open Water Divers. There are no upper age limits.
- Health
You need to be in a state of good health. This doesn't mean you need to be super-fit, but you have to be free of any serious medical problems. You'll answer a medical questionnaire when you sign up for a course and if you or your instructor have any concerns you will be referred to a medical doctor for assessment. You will also need to be able to swim and float or tread water.
- Disabilities
Scuba diving is accessible to people with physical disabilities. Many instructors are trained to provide courses tailored to physically challenged divers and there are diving societies whose primary goal is to facilitate and promote diving for physically challenged people.
What types of scuba diving are there?
There are many types of scuba diving which means there's always something new to do and see. Here are the most popular types:
- Recreational
Most divers are recreational divers and this is the form of diving that is devoted to having fun. Some divers love looking at fish and coral, but there are also many specialized areas of scuba diving. After Open Water certification you can complete courses in all sorts of specialties including, but not limited to: night diving, wreck diving, deep diving, navigation, fish identification, underwater naturalism, photography, videography, cave diving, ice diving, altitude diving, and rescue diving.
- Technical
Some recreational divers want to explore the marine world even further than recreational diving equipment and training allows. Technical diving encompasses areas such as extreme deep diving, advanced wreck diving, and advanced cave diving. Technical diving is for very experienced recreational divers and requires specialised training and equipment.
- Commercial
Commercial divers scuba dive for a living. They build underwater structures such as oil platforms, carry out underwater maintenance, conduct surveys, create maps, participate in salvage operations, and work in many other diving related occupations.
- Military
Military diving is similar to commercial diving but also involves such tasks as underwater surveillance, mine clearing, and military research. Military divers and scientists have historically been responsible for most advances in dive equipment and dive medicine.
Where do people scuba dive?
You can scuba dive anywhere you can find water. Over two-thirds of the planet is covered by water, so you can dive almost anywhere. Tropical coral reefs tend to be most popular amongst recreational divers but there are also many wonderful things to be found in cold water environments such as lakes, rivers, and quarries.
Divers can be found in all corners of the globe from the tropical reefs of the Caribbean and the Great Barrier Reef, to the world's biggest lake in Siberia - even under the ice of Antarctica. While most dive shops and resorts operate in warm tropical environments it's also common to find local dive centers and dive clubs in most cities around the world - even inland cities with no water.
Source: http://scuba.about.com/od/whatisscubadiving/a/About_Scuba.htm
24.11.2010 - Scuba Diving Certification Agencies
You've probably heard of PADI, SSI, NAUI and other scuba certification agencies, but if you don't know the difference between them you're in the right place.
What Does a Certification Agency Do?
In addition to providing all levels of diver training, agencies also regulate and represent diving professionals such as divemasters and dive instructors, regulate dive operators, participate in research in dive medicine, promote marine conservation, and market diving as a sport.
What is the Difference Between the Agencies?
The main difference between agencies is where they operate. Some agencies such as BSAC and CMAS are closely related to their countries of origin, while other agencies such as PADI are truly global organizations. All of the most popular agencies offer very similar courses from beginner through to professional level and will all recognize each other's qualifications at recreational level. They may not recognize each other's qualifications at professional level.
How to Choose an Agency?
When choosing an open water course it's important to remember that all courses are quite similar and an open water certification card from any main agency will be recognized by dive operators anywhere in the world. Your choice of agency should be dictated by which agency is active where you want to learn and which agency your preferred instructor is certified by.
Which are the Biggest Agencies?
PADI has dive centers and instructors almost everywhere people dive and is the biggest agency. Some other agencies such as SSI and NAUI are also wide spread but tend to be concentrated in particular geographical areas. Below is a brief overview of the main agencies. Of course there are many other local agencies that also provide quality training and globally recognized qualifications. You can verify any agency's credentials with the World Recreational Scuba Training Council.
- PADI
The Professional Association of Diving Instructors is by far the biggest and most recognized dive certification agency in the world. It's usually possible to find a PADI instructor in any diving destination and more beginning divers are certified by PADI than by all of the other agencies combined. PADI is very active in marine conservation through their Project AWARE operation, as well as being the biggest promoter of diving through advertising and sponsorship, and is also involved in technical diving training. PADI also operates Emergency First Response, an organization providing CPR and First Aid training.
- SSI
Scuba Schools International's 2000 authorized dealers and 225 Regional Centers can be found in 90 countries around the world. SSI's diver education system is very similar to PADI's system. Headquartered in Colorado, USA, SSI training facilities are in particular abundance in North America and South East Asia.
- NAUI
Founded in 1959 in the USA, the National Association of Underwater Instructors is one of the biggest global certification agencies. NAUI's diver education system is quite similar to SSI and PADI. NAUI has also had a technical diving division since 1997. NAUI dive centers can be found primarily in North America.
- SEI
When the YMCA closed its scuba program of 50 years, Scuba Educators International was formed to continue along similar standards.
- BSAC
The British Sub Aqua Club was formed in the United Kingdom and is still one of the most popular agencies there. It is also possible to find BSAC training facilities in other countries, particularly those that are frequented by British divers. Known for having very high standards of training, BSAC was always known for requiring extreme levels of training to achieve certification. In recent years BSAC has implemented courses that have bought it into line with other agencies training requirements.
- CMAS
Confederation Mondiale des Activites Subaquatiques is the world's oldest scuba certification agency. Originally founded in Brussels, Belgium, CMAS is now headquartered in Rome, Italy. CMAS has quite a different rating system than other agencies that is based on star levels. CMAS can be found in many countries around the world but is primarily active in Europe.
Source: http://scuba.about.com/od/professionalsocieties/a/certagencies.htm
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Image reproduced with the permission of Cressi.
