【How-to】How long can someone hold their breath

VEDANTAM: At 2:00 in the morning on January 8th, 1964, Randy broke the world record. He had gone 11 days, 264 hours, without drifting off. There was only one way to celebrate. He was whisked off to a naval hospital where researchers attached electrodes to his head to monitor his brain waves, and he went to sleep.