magic with water

A magician was boasting one day at how long he could hold his breath under water. His record was 6 minutes. A kid that was listening said, "that's nothing, I can stay under water for 10 minutes using no type of equipment or air pockets!" The magician told the kid if he could do that, he'd give him $10,000. The kid did it and won the money. Can you figure out how?