The writer of this piece spent some time with the captain of the UK freediving team in an effort to live as long as possible without oxygen. Here's what she learned: breathe very slowly for a few minutes before going under, then take one long, deep breath and hold it in. Focus on keeping your diaphragm--your breathing muscle--relaxed, breathing out a little to extend a breath hold until you can't stand it anymore. This skill should come in quite handy in summertime, during those knock-down, drag-out breath-holding contests with the neighborhood kids.