Scuba diving is a mode of underwater diving in which the scuba diver uses a self-contained underwater breathing apparatus (scuba) which is completely independent of surface supply, to breathe underwater. Unlike other modes of diving, scuba divers carry their own source of breathing gas, usually compressed air, allowing them greater freedom of movement than with an air line. Scuba diving may be done recreationally or professionally in a number of applications. A scuba diver primarily moves underwater by using fins attached to the feet. Other equipment includes a dive mask to improve underwater vision, a protective diving 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.
Based on the definition found on Wikipedia: https://en.wikipedia.org/wiki/Scuba_diving