Freediving

Freediving is underwater diving performed on a single breath, without breathing apparatus. It relies on breath-holding, controlled movement, and the body's responses to submersion.

Mammalian diving reflex: A set of physiological responses to submersion that conserves oxygen, including a slower heart rate and blood-vessel constriction. It helps conserve oxygen during a breath-hold dive.
Constant weight apnea: A competitive freediving discipline in which divers descend and ascend using their own propulsion while keeping ballast weight constant. It is a standard discipline for measuring depth under controlled competition rules.
Scuba diving: Underwater diving in which a diver carries a self-contained supply of breathing gas. Scuba supplies breathing gas underwater; freediving depends on a single breath.
Jacques Mayol: A French freediver whose deep dives and public profile helped popularize the sport in the twentieth century. His rivalry with Enzo Maiorca drew attention to competitive depth diving.
Blackout in freediving: Loss of consciousness during or shortly after a freediving breath-hold because of insufficient oxygen. It is a major reason freedivers train and dive with close supervision.
Lung barotrauma: Tissue damage caused when pressure changes injure the lungs. Ascent can expose freedivers to lung injury, especially after deep dives.
Free immersion apnea: A freediving discipline in which competitors pull themselves down and up a line without fins. Line-pulling makes this discipline a distinct alternative to fin-propelled depth dives.
Snorkeling: Swimming at the water’s surface while breathing through a snorkel and observing underwater life. Snorkeling usually keeps the airway connected to surface air, unlike a freediving descent.
Enzo Maiorca: An Italian freediver who set multiple depth records during the sport’s early development. His record contests with Jacques Mayol helped establish freediving as a public sport.
Freediving training: Preparation for breath-hold diving through technique, conditioning, and safety education. Training emphasizes conservative limits and rescue skills as well as performance.

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