Freediving

Competitive freediving involves descending to extreme depths on a single breath, without scuba equipment, relying entirely on breath-hold technique and physiological adaptation. In the "No Limits" discipline — now banned from records due to safety concerns — Austrian Herbert Nitsch reached 253.2 metres (830 feet) in 2012, nearly dying from decompression sickness on the way up. The constant-weight discipline record stands at 130 metres. Shallow-water blackout — sudden loss of consciousness near the surface caused by hypoxia — is the leading cause of death in recreational freediving, claiming an estimated 5,000–7,000 lives per year worldwide.