I am here to say it is impossible to hold one's breath for as long as David Blaine claimed. The clues to it being an illusion are the shape of the tank (What is the difference between a sphere and a cube?); he provided his own water (curious,eh?... like Oprah didn't have water); his heart rate didn't decrease for all his meditation (as seen in any Indian guru worth his salt); he had a heart rate monitor, but not a breathing monitor; he wore a very stiff wetsuit (around the chest); he is an illusionist; and, the clincher, I saw a (video recorded) mouse in a beaker do the very same trick many years ago with no training or meditation. Oh, yeah, the "water" was cold, but that wasn't the only reason for the wetsuit. Would he need to train his chest muscles? Yes, but not for the reasons most people think.
What was said on Oprah was technically correct (at least for the most part, as much as I watched.) Have no doubt, what he did was dangerous. The little mouse experiments had one nasty side effect... the animals tended to die after they were withdrawn from the liquid. These days, the submersion technique has been used in experimental medical practice. It is VERY expensive and dangerous, but better than the early days. The expense of David's illusion wasn't in the tank, but in the "water."
After his Oprah appearance, I wrote on her discussion group about why it wasn't real (without giving away his illusion) and caused a real furor among true believers of the silly stuff, then left town to be with my ill son. When I came back, there were messages from her producers wanting me to be either on the show or at least in a discussion (I can't remember which.) Too bad, I was too late.
I did write to one of her producers and tell them specifically how the illusion was done, but did not post it in the forum. Although David Blaine did perform an illusion, I think it was inventive and imaginative. That was the same thing I thought when I saw the mouse do it... cool, it would make a good trick! I guarantee you that if you tied a cement block to Blaine's feet and tossed him into the deep end of a regular pool, like in Sopranos, oxygen loading or not, he'd be clawing for the surface and sputtering in no time.
My background includes a Biology degree, scuba diving, former distance runner (for fun) and, decades ago, being a dabbler in "magic." To find the answer, keep in mind it is IMPOSSIBLE to hold one's breath as long as he claimed (especially when the heart is beating like a teenage boy seeing a cute girl). I think half the fun of illusions is figuring out how they are done.
). I tried watching for any signs of movement in the video clip, but it was rather short to determine (how many times did he raise his arms? I'm wondering if that was a cover for taking a breath). 
