Free diving is a form of underwater diving that relies on breath-holding until resurfacing rather than the use of breathing apparatus such as scuba gear.Besides the limits of breath-hold, immersion in water and exposure to high ambient pressure also have physiological effects that limit the depths and duration possible in freedivi.Examples of freediving activities are: traditional fishing techniques, competitive and non-competitive freediving, competitive and non-competitive spearfishing and freediving photography, synchronized swimming, underwater football, underwater rugby, underwater hockey, underwater target shooting and snorkeling. 

A freediver breathing pure oxygen for 5 minutes at a depth between 4 to 6 meters at the end of a dive session would thus highly reduce his risk to suffer DCS. In most freediving competitions oxygen is now available to divers diving deeper than 70-80 meters.