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Scuba Diving

Scuba Diving

The word "scuba" stands for "self contained underwater breathing apparatus". This device allows persons to dive underwater for extended periods of time. The most popular form of this apparatus is called an aqualung, which was designed in France during World War II by Jacques Yves Cousteau. Jacques Yves Cousteau was a French navel officer when he developed the aqualung. He is most famous for his work as an underwater explorer. The aqualung consists of anywhere from one to three cylinders of compressed air that is fed to an underwater diver through a mouthpiece.

Persons wishing to take up the sport of scuba diving need to be properly trained. There are several organizations that provide training and certification in this sport, including the National Association of Underwater Instructors (NAUI) and the Professional Association of Diving Instructors (PADI).

Because of the potential hazards of scuba diving, instructors spend much of their time teaching proper safety techniques. This requires a full understanding of the operation and proper maintenance of diving equipment as well as an understanding of the effects of underwater pressure on the human body. At sea level, the air pressure on the body is 14.7 pounds per square inch (this is the equivalent of 1 atmosphere). Every time a diver descends 33 feet underwater, the pressure increases by an additional 14.7 pounds per square inch.

"The bends," or decompression sickness, is one such hazard associated with pressure changes. The longer you stay down and the deeper you go, the more nitrogen dissolves into your body tissues. If you ascend too rapidly, the dissolved nitrogen comes out of solution too quickly and forms bubbles in your tissues. A diver suffering from decompression sickness can experience severe pain (particularly in joints), dizziness, and in severe cases, blindness, paralysis, and death.

Because of these safety concerns, the NAUI, using information provided by the U.S. Navy, has created dive tables that specify how a given dive needs to be approached. Prior to any dive, several variables need to be considered. These variables include dive schedule (this includes information about depth and dive time), maximum dive time (MDT), actual dive time (ADT), residual nitrogen time (RNT), and total nitrogen time (TNT). Using these variables and the NAUI dive tables, a person can determine how a dive must be approached. For example, the tables will provide information about how long a given dive can last as well as how much time needs to elapse before a second dive can be initiated. This time between dives, called surface interval time (SIT), allows for excess nitrogen in the system to dissolve. All nitrogen leaves the body after 24 hours. If a person makes a second dive in less than 24 hours time, another table needs to be consulted, based on the fact that nitrogen is still in the body.

In addition to the information provided by the tables, other rules or standards must also be applied. For instance, all divers must ascend no faster than 60 feet per minute. Also, the depth of a dive must always be considered as the deepest depth attained, even if the majority of the dive time is spent at a lesser depth. When scuba divers plan dives that are particularly cold or strenuous, additional precautions must be followed.