When I saw him on the bottom, I immediately knew something was wrong and dove in to get him. He was blue, convulsed with eyes wide open and not breathing when I got him out of the water. Fortunately, I was able to resuscitate him without any permanent physiological damage, although he was taken to the hospital for observation and his chest hurt for several days from water in the lungs. Unfortunately, Ortega's coaches, friends and family weren't so lucky. Shallow Water Blackout is most commonly associated with skin diving, but the more swimming coaches I speak with, the more I have come to realize that underwater fainting is not at all uncommon in the world of competitive aquatic sports.
Individuals breathing under normal conditions use the partial pressure of oxygen in the lungs.
Carbon dioxide, on the other hand, serves as a stimulus to breathing by informing the brain that a person's body requires another breath of air. This process occurs in any prolonged holding of breath, including underwater swimming. Normally there is no danger because the carbon dioxide build up in the blood signals the brain that you need to take a breath by giving you the sensation that your lungs are going to burst if you don't get a breath. Hyperventilation is the repeated inhalation of fast, full breaths of air and rapid exhalation. The effect of hyperventilation is to wash C02 out of the lungs, resulting in an extremely low C02 level.