the activity or sport of swimming as deep as you can under water without using breathing equipment

In freediving the diver descends with no more than a lung full of air, to depths of up to 100 metres. 在自由潜水过程中，潜水员可以仅仅凭借自己肺里的空气下潜到100米深的水下。

Deaths in competition free-diving are rare but happen occasionally. 自由潜水比赛中死亡很少见，但偶尔也会发生。