FreeDiver Missing and Presumed Drowned

[MAXFACTOR]

I read this on the CDNN site the other night. 

Maybe one of you free divers can answer this....

I just do not understand why you would want to purposely hperventilate yourself to the point of being just about  dizzy, and then making the dive.

I fully understand the part of getting as much oxygen in your blood stream, but not to the point of near black out.  I've watched the free divers do this and I know it works, but it seems very risky. 

Have any of you free divers experienced shall water blackout, and found yourself awaken under water?  I'm not sure if this is the right terminology for the sport, but from a lay position, that is what it seems like what happens.

If so,  how then do you know where the heck you are and for how long you've been blacked out?  Are you really able to gather your thoughts to look at your computer and remember the start time and current dive time etc.


Maybe I just have to do some more reading on it, but as I don't have a real interest in free diving, I just haven't taken the time to read up on it. 
thanks in advance

MAXFACTOR