Scuba diving

Scuba diving is a mode of underwater diving in which divers use breathing equipment that is completely independent of any surface gas supply, so their endurance is limited but variable. The word scuba stands for self-contained underwater breathing apparatus and was coined by Christian J. Lambertsen in a patent submitted in 1952. Carrying their own gas gives divers more freedom of movement than surface-supplied divers and more time underwater than freedivers. Open-circuit systems release exhaled gas into the water and use cylinders of high-pressure gas delivered through a regulator, while closed-circuit and semi-closed rebreathers recycle exhaled gas for longer dives with fewer bubbles and less noise. Scuba is done recreationally and professionally, in scientific, military and public safety roles. Divers move mainly with fins, wear a mask, a diving suit, ballast weights and buoyancy control gear, and learn standard and emergency procedures from instructors affiliated with the certification organizations.