Scuba & Snorkeling

A scuba set is any breathing apparatus that is carried entirely by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment which is required for providing breathing gas to the diver, general usage includes the harness by which it is carried, and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge, and in the looser sense it has been used to refer to any diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface supplied diving systems, and is allowed by the relevant code of practice. Two basic functional systems of scuba are in general use: open-circuit-demand, and rebreather. In open-circuit demand scuba, the diver expels exhaled air to the environment, and requires each breath be delivered on demand by a diving regulator, which reduces the pressure from the storage cylinder. The breathing air is supplied through a demand valve when the diver reduces the pressure in the demand valve during inhalation In rebreather scuba, the system recycles the exhaled gas, removes carbon dioxide, and compensates for the used oxygen before the diver is supplied with gas from the breathing circuit. The amount of gas lost from the circuit during each breathing cycle depends on the design of the rebreather and depth change during the breathing cycle. Gas in the breathing circuit is at ambient pressure, and stored gas is provided through regulators or injectors, depending on design. Within these systems, various mounting configurations may be used to carry the scuba set, depending on application and preference. These include back mount, which is generally used for recreational scuba and for bailout sets for surface supplied diving, side-mount, which is popular for tight cave penetrations, sling mount, used for stage-drop sets, decompression gas and bailout sets where the main gas supply is back mounted, and various non-standard carry systems for special circumstances. The most immediate risk associated with scuba diving is drowning due to a failure of the breathing gas supply. This may be managed by diligent monitoring of remaining gas, adequate planning and provision of an emergency gas supply carried by the diver in a bailout cylinder or supplied by the diver's buddy.
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