Scuba-diving involves the voluntary immersion of a person in salt or fresh water. The acronym SCUBA stands for Self Contained Underwater Breathing Apparatus and refers to the fact that a diver has an independent source of air while underwater (see Cousteau, Jacques-Yves).
Scuba-diving is a relatively equipment-intensive recreational activity, and a standard set of equipment includes: mask, snorkel and fins; a dry or semi-dry suit or wetsuit, sometimes with a hood, depending on the water temperature and the length and depth of the immersion. A belt with lead weights around the diver’s waist, attached with a quick-release buckle, is necessary for submerging; otherwise the body, including equipment, would float - being lighter then water. Scuba-divers require items that permit them to breathe under water: a metal tank, mostly cylindrical, which holds high-pressure/compressed air for breathing, is usually attached to a ‘vest-looking’ buoyancy control device (BCD), which can be inflated and deflated by the diver to maintain the required buoyancy. A hose is attached to the tank through a first stage - which lowers the air pressure - and leads the still compressed air to the regulator (called a second stage).
The second stage transforms the high-pressure air into breathable air at the external pressure, so that the diver can inhale it. An alternate air source is strongly recommended, and usually there is a spare second stage called an ‘octopus’. In order to safely adapt to the underwater world it is necessary to keep track of: (i) the amount of air left in the tank, using a mandatory submersible pressure gauge (SPG); (ii) time, using an underwater timepiece, such as a diver’s waterproof watch; and (iii) depth, through a depth gauge. Dive tables allow calculations for changes to pressure on body and gas dispersal, providing for safe dive planning. Most of the equipment can be hired from scuba-diving schools, which also provide training for recreational diving, inclusive of certification.
The Professional Association of Diving Instructors (PADI), Confederation Mondiale Des Activites Subaquatiques (CMAS), the National Association of Underwater Instructors (NAUI) and Scuba Schools International (SSI) are among the leading dive organizations. PADI estimates that there are between 5 and 7 million active divers worldwide, making scuba-diving one of the world’s most popular leisure adventure activities. Lists of ‘top ten’ diving destinations worldwide consistently include Pacific Ocean coasts, and islands in the Red Sea and the Caribbean.
Diving experiences often begin with a ‘one-off’ introductory or resort scuba-dive under the strict supervision of an instructor. This experience involves a medical screening questionnaire, some basic theory and time underwater to a maximum depth of 10 m. The experience does not result in a licence to dive independently. For that, an Open Water Certification course is required. Three to four days is the average time to earn a certification (called a ‘C’ card). The course provides some theoretical knowledge, confined water training and open water training. With a C-card divers can hire diving equipment and dive in buddy pairs to a recommended depth of 18 m. The certification does not expire, although training updates and medical checks are strongly advised.
With an Open Water Certification divers can enrol in speciality courses, the most popular being Deep Diving, Night Diving and Underwater Photography. The main prerequisite for any dive or dive course is a basic degree of health and fitness. Health issues that will prevent an individual from diving include asthma, epilepsy and heart and upper respiratory track conditions. Recognizing the inherent risks in underwater activities, some groups like Divers Alert Network (DAN) and South Pacific Underwater Medicine Society (SPUMS) contribute to the health and safety of scuba-divers through medical research.
See also: Decompression Illness.
CMAS (Confederation Mondiale Des Activites Subaquatiques): http://www.cmas.org
DAN (Divers Alert Network): http://www.diversalertnetwork.org
NAUI (The National Association of Underwater Instructors): http://www.nauiww.org
SSI (Scuba Schools International): http://www.ssiusa.com
SPUMS (South Pacific Underwater Medicine Society): http://www.spums.org.au
PADI (Professional Association of Diving Instructors): http://www.padi.com
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