The exhilarating freedom of breathing underwater is the main draw for many people who choose to become scuba divers. However, diving is a dangerous sport and should only be attempted after proper training and knowledge of the risks are obtained.

The equipment used by scuba divers consists of one or more tanks containing compressed air; usually ordinary air for most dives but for longer dives a mixture of air containing less nitrogen (nitrox) is used to prevent decompression sickness, sometimes called the bends. The tank is attached to a buoyancy control device (BCD), which allows the diver to maintain neutral buoyancy at a chosen depth by adding or removing air from an inflator valve. The BCD also has a dump valve which, when opened, allows the diver to quickly ascend to the surface.

Other essential pieces of diving equipment are the dive computer, which records and displays the dive profile, a buddy indicator to warn the other diver if the first diver is close enough to touch, and a capillary depth gauge which uses Boyle’s law to determine the actual dive depth. In addition, all scuba divers carry an emergency bailout scuba supply which they can use to continue breathing in the event of a loss of primary scuba gas supply at depth.

The most serious scuba diving emergencies are the result of running out of breathing gas at depth. This can be handled in several ways including sharing oxygen with a buddy or carrying an independent alternative air source.