Freediving

Underwater diving without breathing apparatus

Freediving, free-diving, free diving, or breath-hold diving is a mode of underwater diving that relies on breath-holding (apnea) until resurfacing rather than the use of breathing apparatus such as scuba gear. Historically and colloquially, the term skin diving has been used interchangeably with freediving. However, in modern and recreational context, skin diving generally refers to recreational breath-hold diving at shallow depths to observe marine life, whereas freediving is recognized as a distinct discipline focusing on maximizing underwater breath hold duration, depths, or distance.

From Wikipedia, under CC BY-SA. More on occurri.