Sandra Ireland is an 18 year old competitive underwater swimmer at an important swim meet. In underwater swimming, the swimmer who can swim the farthest without coming up for a breath wims. Immediately prior to the start of the competition, Sandra breathes rapidly and deeply for 2 minutes. She dives into the pool, and swims almost 150 metres (without coming up for air). Sandra then appears to lose consciousness in the pool. Lifeguards in attendance pull her out and perform basic resuscitative measures. Three minutes later she is awake and breathing on her own.