Freediving

Freediving is a breath-hold descent to extreme depths without scuba equipment, relying entirely on physiological adaptation and mental discipline. In the now-banned "No Limits" discipline, Austrian Herbert Nitsch reached 253.2 metres (830 feet) in 2012, nearly dying from decompression sickness on ascent. The constant-weight record stands at 130 metres. Shallow-water blackout — sudden hypoxia-induced unconsciousness near the surface — causes an estimated 5,000 to 7,000 deaths per year globally.