The brain uses 25% percent of all the oxygen in the body. It can survive up to 6 minutes without it before it begins to suffer irreversible damage. Such damage can put a person in a vegetative state where bodily functions still exist but the person is unresponsive. In 1983, Ray Parrish (35) lived after 20 minutes under the Mississippi river. He survived with no brain damage nor health problems. When he was rescued, he was unconscious and he was swollen to the point that every facial feature was indecipherable. His amazing story is proof at how amazing the human body is.