Scuba, an acronym for Self-Contained Underwater Breathing Apparatus, is an activity that involves breathing air from a tank while underwater. Many people enjoy scuba diving recreationally, for example to explore ship wrecks or swim in kelp forests and coral reefs or just to see fish up close in their natural habitat. Other people use scuba skills in their work as professional divers, such as public safety divers or marine biologists.

A scuba diver typically wears a wet suit, snorkel, mask and fins. A scuba diver can also choose to add a dive computer and air tank. The dive computer monitors and controls the diver’s residual inert gas and records dive profiles that can be used for planning future dives.

The scuba mask and fins are designed for easy mobility in the water, while the wet suit provides insulation from the colder temperatures of deeper waters. A scuba tank holds the diver’s source of life-giving air, and is a vital piece of equipment that must be carefully maintained.

The most serious scuba emergency is running out of breathing gas under water, often called “out-of-air” or OOA. This is a very dangerous situation as without access to breathing gas the diver will die within minutes. Divers can respond to OOA by requesting assistance from a buddy, or by providing themselves with an alternative breathing gas source (bailout), such as a spare tank. It is important for every diver to learn how to respond to an out-of-air incident.