Saw a promo last night for David Blaine's new show. Apparently he will be underwater for 9 minutes. I don't believe it can be done. So I looked it up:
Brain cells are extremely sensitive to oxygen deprivation and can begin to die within five minutes after oxygen supply has been cut off. When hypoxia lasts for longer periods of time, it can cause coma, seizures, and even brain death. In brain death, basic life functions such as breathing, blood pressure, and cardiac function are preserved, but there is no consciousness or response to the world around.
Yet, there are some people who have done such a thing. This video shows the women's world record holder for static apnea at 6:13. I did not watch the whole thing. The world record is 8:58. Your heart rate drops to less than 30 BPM.
Will I watch Blaine? No.