OPEN YOUR MOUTH, and you’re dead. “How deep can they go? Nobody knows. Competitive freediving is a relatively new sport, and since the first world championships were held in 1996, records have been broken every year, sometimes every few months. Fifty years ago, scientists believed that the deepest a human could freedive was about 160 feet. Recently, freedivers have routinely doubled and tripled that mark.” Yeah, I was talking with a freediving instructor on Cayman a couple of years back and he said he could have me diving that deep (150 feet) in a couple of days. But I stuck with scuba.