I tripped across this article concerning the 2011 Free Diving World Championships.
It's a long article, but, I think, well worth your time. Very interesting.
These guys (and girls) are nuts if you ask me.
Open Your Mouth, And You're Dead
, from outsideonline.com.
“Blow on her face!” yells a man swimming next to her. Another man grabs her head from behind and pushes her chin out of the water. “Breathe!” he yells. Someone from the deck of a boat yells for oxygen. “Breathe!” the man repeats. But Kitahama, who just surfaced from a breath-hold dive 180 feet below the surface of the ocean, doesn’t breathe. She doesn’t move. Kitahama looks dead.
Moments later, she coughs, jerks, twitches her shoulders, flutters her lips. Her face softens as she comes to. “I was swimming and…” She laughs and continues. “Then I just started dreaming!” Two men slowly float her over to an oxygen tank sitting on a raft. While she recovers behind a surgical mask, another freediver takes her place and prepares to plunge even deeper