The diver under great pressure to hit new lows

Freediver William Trubridge. Photo / Igor Liberti

Often claims of superhuman feats on the sports field amount to media hyperbole.

But when New Zealand free diver William Trubridge this week became the first man to dive to a depth of 100m unassisted, there was never any danger of over-embellishing his achievement.

The 30-year-old broke his own world record of 95m, diving unassisted to reach the mark set in 1980 by Jacques Mayol. But whereas Mayol used a weighted sled to descend and an inflated lift bag to return to the surface, Trubridge relied on his hands and feet to propel him through the depths.

The total time under water on a single breath and in constant motion was 4 minutes, 10 seconds. That in itself is a phenomenal physical achievement but the physiological issues that occur at that depth - and while losing oxygen - make this a truly superhuman feat.

The pressure exerted by water at depths approaching 100m is around 16.5kg/cm2 and is so great that free divers' lungs can be crushed to the size of a small grapefruit.

Then they have to worry about how they're going to get back to the surface.

At that depth Trubridge would have been unable to see the surface, but running out of air, he had to get there fast and without creating embolisms in the blood due to rapid decompression.

Given it is such an extreme physical endeavour, there was more than a hint of frustration from Trubridge when he reached the same depth the day before, but had his dive disallowed through a minor technicality with his surface protocol (where divers have to prove to the judges they are lucid).

Trubridge reached the 100m mark and surfaced cleanly, but forgot to remove his nose-clip before signalling to the judges that he was okay.

"It was frustrating but the rules are there for our safety so we have to follow them to the letter."

There was another hiccup with his second attempt the next day after a poor start forced him to resurface.

After a short break Trubridge tried again, this time making no mistake.

But he remembers very little of his world record dive, with his body going onto "autopilot" and muscle memory taking over. Once the dive was complete, it took some time for the weight of the achievement to sink in for Trubridge.

"I guess it took a while to set in. The initial moment when you hit the surface the dive isn't fully over because you still have to do your surface protocol. But once I got the white card from the judges and everyone starting celebrating all at once, that's when it became real for me."

Trubridge had been training fulltime for the 100m attempt since May, with many hours spent in the gym and the pool before he even started his depth training.

Along with extreme physical fitness, free divers also require strong mental discipline and Trubridge believes this is where yoga techniques help.

But just how does one hold one's breath for over four minutes?

"The main thing with the preparation is to get as relaxed as possible," said Trubridge. "I lie next to where I'm going to be diving in the water and just try and slow my breathing down, breathing as naturally as possible and just trying to relax my muscles so when I start the dive I have as much oxygen in the body as I possibly can."

But it takes more than a healthy set of lungs to be a successful free diver. Trubridge says the key is being comfortable in the water and believes his childhood spent in and around the water helped groom him for his sport.

"I think it's more important to be at home in the water, to feel like the liquid element is another natural place to be and unless you have that then no amount of genetic lung volume or anything like that is going to allow you to be able to dive deep."

And Trubridge is hoping to reach even further dizzying depths. Now he has reached the magical 100m mark unassisted, he plans to switch his focus to the fin discipline, which has a world record of 124m.