WHAT IS SCUBA DIVING?

Scuba diving is a mode of underwater diving in which a scuba diver uses a self-contained underwater breathing apparatus (scuba) to breathe underwater. Unlike other modes of diving, which rely either on breath-hold or on breathing gas pumped from the surface, scuba divers carry their own source of breathing gas, usually compressed air, allowing them greater freedom of movement than with anair line or diver's umbilical and longer underwater endurance than breath-hold.

Scuba equipment may be open circuit, in which exhaled gas is expelled to the surroundings, or a closed or semi-closed circuit re-breather, in which the breathing gas is scrubbed to remove carbon dioxide, and the oxygen used is replenished from a supply of feed gas before being re-breathed. Scuba diving may be done recreationally or professionally in a number of applications, including scientific, military and public safety roles, but most commercial diving uses surface supplied diving equipment when this is practicable.

A scuba diver primarily moves underwater by using fins attached to the feet, but external propulsion can be provided by a diver propulsion vehicle, or a sled pulled from the surface. Other equipment includes a dive mask to improve underwater vision, a protective dive suit, equipment to control buoyancy, and equipment related to the specific circumstances and purpose of the dive. Scuba divers are trained in the procedures and skills appropriate to their level of certification by instructors affiliated to the diver certification organisations which issue these certifications.