Top athletes of free diving on 60 Minutes

There are people who can dive deeper than WWII submarines without coming up for air, in the increasingly popular extreme sport called free diving. Bob Simon speaks to two of the sport's top performers for a 60 Minutes story that will bring viewers hundreds of feet under the sea, where records are being broken and lives risked. Simon's story will be broadcast on 60 Minutes Sunday, Jan. 13 at 8:00 p.m. ET/PT.

Two years ago, one of the world's top free divers, New Zealander William Trubridge, broke records by venturing down to 331 feet without swim fins. Asked by Simon if, at the time, anyone thought such a deep dive was possible without fins, Trubridge replies, "When the record was 80? I don't think so. I don't think anyone realistically thought it was going to happen or at least not soon."

No one yet knows how deep free divers will be able to go. "It's out there but there's no way...of knowing exactly where it is. It's just deeper than we are now, we know that much," Trubridge tells Simon. 60 Minutes cameras will follow Trubridge on another record attempt at the sport's Mecca in the Bahamas, Dean's Blue Hole, a limestone pit hundreds of feet deep. The results will be revealed Sunday night.

The divers who perform such feats are highly conditioned athletes. They've perfected exercises that streamline the body for swimming and, of course, breath-holding. The pressure at those depths usually causes disorientation, which increases the danger of the sport.

Free divers have died in pursuit of records, often because they pass out on the way back up.

Why do they do it at all? Tanya Streeter, one of the greatest female free-divers, who once went down more than 500 feet, says it's a deeply personal experience for her. "It's just a little bit difficult for people to fathom, if you excuse the pun," she tells Simon with a laugh. "But it's what I love to do...we don't dive to look around us, we dive to look within ourselves. It's a journey of self-exploration," she says.