That's How It Happened

In case you hadn't heard, via every news source in the Western hemisphere, David Blaine is spending 7 days underwater, before breaking the world record for static breath holding (currently 8mins 58 secs), while escaping from a set of chains. Despite the fact that Blaine has been "training exhaustively with the Navy SEALS", and has "lost 50lbs in weight in order to reduce oxygen consumption", it ought to seem implausible to you that a celebrity magician could break a highly competitive world record. That's because he's going to cheat. You don't need a PhD in diving medicine to figure out how.
If you can't stand maths, skip this bit, but it's pretty easy:
Resting oxygen consumption for a 70kg adult = approx 0.2l/minute
Total lung volume for said adult = approx 4.5l
% of oxygen available to dissolve into blood during prolonged breath holding = more than 80%
(80% x 4.5)/0.2= 18 minutes
Essentially nine minutes is a grossly conservative estimate for how long you can hold you breath if you fill your entire lung volume with 100% oxygen. There is a risk though. Without any CO2 to warn him when he really needs to breathe, Blaine is at risk of a shallow water blackout. My guess is that he has practiced the timing of the stunt quite carefully. Conceivably he even has a pulse oximeter clipped onto one of his gonads, so he can tell when hypoxia is ensuing. Either way it's a stupid con, and he won't be getting his name in Guinness for this.

Tags: davidblaine, howto