Remove, Replace and Clear a mask's scuba diving skill demonstration by PADI CD Alain Barrat

Scuba diving is a form of underwater diving in which a diver uses a self contained underwater breathing apparatus (scuba) to breathe underwater.[1]

Unlike other modes of diving, which rely either on breath-hold or on air pumped from the surface, scuba divers carry their own source of breathing gas, usually compressed air,[2] allowing them greater freedom of movement than with an air 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 rebreather, 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.

A scuba diver usually moves around 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.