Scuba diving is a mode of underwater diving whereby divers use breathing
equipment that is completely independent of a surface breathing gas
supply, and therefore has a limited but variable endurance. The name
scuba is an anacronym for "Self-Contained Underwater Breathing
Apparatus" and was coined by Christian J. Lambertsen in a patent
submitted in 1952. Scuba divers carry their own source of breathing gas,
usually compressed air, affording them greater independence and movement
than surface-supplied divers, and more time underwater than free
divers.Although the use of compressed air is common, a gas blend with a
higher oxygen content, known as enriched air or nitrox, has become
popular due to the reduced nitrogen intake during long or repetitive
dives. Also, breathing gas diluted with helium may be used to reduce the
effects of nitrogen narcosis during deeper dives.
Learn more on Wikipedia 🤓