"Sometimes if I'm taking my last breath, a voice will pop into my mind saying, 'This could be your last breath of your life.'"
That's what champion free diver William Trubridge told 60 Minutes in the 2013 story posted in the video player above. Trubridge said he was well aware of the dangers of free diving, an extreme sport in which athletes plunge hundreds of feet beneath the surface of the ocean on a single breath.
Last weekend, Trubridge broke his own world record, diving 122 meters -- or 400 feet -- on Saturday. Then, during an unplanned dive on Monday, he beat his record again, holding his breath for four minutes and 34 seconds to dive 124 meters.
Trubridge's records are in what's called "free immersion" diving, when divers without fins pull themselves down into the ocean depths and up again along a weighted rope.
While free diving might sound unnatural, 60 Minutes reported, its enthusiasts are quick to point out that humans spend their first nine months before birth surrounded by amniotic fluid. Newborn babies are automatically able to swim and hold their breath.
What's more, scientists who have studied free diving have found that humans have dolphin-like attributes that enable us to survive in the water. When we enter cold water, a reflex kicks in which slows down our pulse, and shifts blood from our extremities to our heart and brain. Our spleen contracts, releasing oxygen-rich blood into our arteries.
But what's the appeal of forcing your body into oxygen deprivation in the first place? Trubridge described free diving as a sort of oneness with nature.
"You're alone with yourself down there at depth," he told Bob Simon. "Even your body slips away so that it feels like you're just a kind of a speck of consciousness that's floating into the abyss. You're weightless. There's no light, no sound and so it's almost as if you're floating in a completely empty tank."
60 Minutes visited Dean's Blue Hole in the Bahamas, where Trubridge lives and works. He owns a diving school called Vertical Blue that also hosts many of the sport's top competitions. Our cameras rolled as Trubridge prepared himself for a dive, doing exercises to make his body more flexible and supple, and then literally gulping air to expand his lungs to the size of watermelons.
During that dive, Trubridge made it all the way down to 410 feet on a single fin, but he failed a basic cognitive test when he surfaced, invalidating his record-setting time. So much training for nothing, yet he was still smiling when Simon interviewed him afterwards.
"I feel good because I know I can do it again," he said. "It might not be for a while, but I can definitely do that depth."
The increasing popularity of the sport and the urge to go ever deeper has already claimed some victims. Nicholas Mevoli, a 32-year-old from Brooklyn, New York, died during a record attempt in November, 2013.
"Isn't there a certain limit of underwater that's just -- you can't go beyond it without dying?" Simon asked Trubridge.
"Definitely," Trubridge said. "It's out there, but there's no way of kind of knowing exactly where it is. It's just deeper than we are now. We know that much."