William Trubridge stops inhaling, rolls gently to his left and begins his plunge to a depth where light, sound and smell do not penetrate. He gives Dylan Cleaver the low-down on his freediving feats.

When William Trubridge descended a world record 102m into the deadening silence of Dean's Blue Hole it was the culmination of two years' planning.

Armed only with two oxygen-thirsty lungs, Trubridge submerged himself, returning to the surface four minutes and 14 seconds later.

The dive, in July, was hailed as a triumph of the human spirit, a win for mind over matter and a cosmic feat of spiritual oneness with the ocean - a place where, as if we needed reminding, humans are not physiologically equipped to survive.

In reality, Trubridge achieved nothing except for adding a metre to his own world record and changing perceptions of what might be possible with the right training and in the right conditions.


Strip it back to its essence and it was a very scientific feat.

It's okay to feel like it was something more, though. It's been 63 years since humans went as high as they could go while staying connected to this planet, so in many respects the deep blue yonder is the final frontier and, hey, it's great that it's once more a New Zealander pushing those limits further than anybody else.

This is a short story about a deep subject, so let's take the plunge.


Trubridge is on his back, with the aid of floatation devices, above the second-deepest saltwater blue hole in the world, which sits in an otherwise shallow bay off Long Island in the Bahamas. He is tethered to the line where, 102 metres, or 334 feet six inches below, tags sit upon a metal plate. Returning one to the surface will prove his feat was more than a figment of our imagination.

He is "breathing up", the process of filling his lungs with the oxygen that will sustain him for the minutes he will be unable to inhale.

The average set of lungs have capacity for about six litres of air. Controversial Cuban freediver Pipin Ferreras was said to have capacity for 8.2 litres, a figure Trubridge believes could be counter-productive for his favoured Constant Weight No Fins (CNF) category of diving.

"My lungs are average size," he says. "Okay, they might be a smidgen bigger than yours but bigger lungs are not necessarily an advantage. If you think about it, it's like carrying two balloons with you to the bottom."

Rather than having extraordinary lung capacity, it is more energy efficient to store the oxygen in your tissue through myoglobin, the oxygen-carrying pigment of muscle tissue found in high concentrations in diving mammals. Myoglobin is the magic protein that allows whales and seals, for example, to hold their breath under water for long periods of time.

Right now Trubridge is not thinking about ocean mammals. He's really trying to think of nothing except the fact he will soon stop inhaling, roll gently to his left and begin his plunge to a depth where light, sound and smell do not penetrate, effectively shutting down three senses.

As a final act of oxygen engorgement, he starts "packing", the art of forcing more air into your trachea with your tongue. To a layman it looks, as Trubridge remains on his back, a little like a fish gasping for water when it is brought on to a boat.

"It's a technique you only teach advanced divers," the 36-year-old says. "It's the cherry on top, but it can be dangerous."

The increase in air can cause the alveoli - tiny sacs in the lungs - to swell and air to escape into the lung cavity. Experienced freedivers can usually cope with this, but in extreme cases it can cause a collapsed lung.

Trubridge's final breath, from the beginning of the inhalation to the completion of 'packing', can take more than half a minute.


As Trubridge descends, the principles of Boyle's law start to apply.

The law says the pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and volume remain the same within a closed system. The simplest way to grasp this concept is to put your finger over the end of a bike pump but still depress the pump. There's now less volume in the canister, but the external forces exerted mean a whole lot more pressure trying to get out to equalise.

As Trubridge descends, the pressure around him grows and the volume of his lungs decreases in proportion to the increase in pressure. On the surface, the normal atmospheric pressure is 100 kilopascals.

"At 10m the pressure is doubled," Trubridge says. "The deeper I go the more compressed the air becomes."


To this point, Trubridge has been making long strokes with a frog-like two-footed kick. It's a slower, more graceful version of Patrick Duffy's Man From Atlantis. This technique has been honed over hundreds of dives to the point where it is second nature.

On deep descents, Trubridge cannot be thinking about technique, worrying about whether he is doing it right. It has to be a "form of auto-pilot".

At these depths buoyancy is still your enemy, something to cut through without expending too much energy or raising the heart rate, which in turn burns oxygen.

The pressure is now trebled, meaning the volume of air in his lungs has been squeezed to 33 per cent of the size it was on the surface.

At 23m, Trubridge takes his last stroke on the downward leg as negative buoyancy kicks in. An extremely simple law will guide Trubridge the rest of the way to 102m: gravity.

"Crossing over to freefall is the most enjoyable phase of the dive, but it can be a double-edged sword. For the inexperienced diver, this part can be quite disconcerting.

"Once you learn to relax here and allow gravity to take over, it is a nice feeling."


We should probably talk more about equalising here. Most of us have had that uncomfortable feeling that our ears are about to burst while sitting in pressurised aeroplane cabins while ascending to, or descending from, an altitude of around 10km.

Considering the external pressure exerted on Trubridge's body is now at 400kPa, reducing the volume of air in his body to 25 per cent of what it was on the surface, he must be equalised.

There are a variety of different methods: The basic Valsalva manoeuvre - close your lips and pinch your nose while trying to force an exhale - which works only at relatively shallow depths; the popular Frenzel technique, which effectively uses the tongue as a paddle to force air into the cavities; or the tricky, French-navy inspired beance tubaire volontaire or BTV manoeuvre. The best freedivers tend to individualise their techniques.

"I shift air by using my tongue like a piston," Trubridge says.

The importance of equalising cannot be downplayed. Any diver that fails to equalise before the pain hits is almost forced to abort his or her descent.

A failure to do so can rupture the eardrum, causing painful and possibly permanent damage, and create something called sinus squeeze, which can lead to skull defects.

40m to 100m

The top 200m of the ocean is known as the euphotic zone. This is the depth to which sunlight generally penetrates and where the bulk of the world's commercial fish species live.

Because Dean's Blue Hole is, well, a hole, natural light does not penetrate as far (though because this is a made-for-TV event, there are powerful lamps that enable us to witness his descent).

Still, it is dark. With darkness and discomfort can come, surely, dark thoughts?

"Do you feel anxiety? Yes and no," says Trubridge. "It's not caused by the sensation of danger and risk. If you want to call freediving an extreme sport, well it's at the safer end of those sports because of the systems in place.

"You can black out under water and you'll be brought to the top and no harm will come to you."

Still, athletes die doing this sport, most famously Audrey Mestre, girlfriend of Ferreras, who couldn't be resuscitated after the air bag, that was meant to propel her back to the surface after a weighted sled had taken her to 171m below in an attempt at a no-limits world record, failed to inflate.

Yet Trubridge says he never worries that the breath he just drew on the surface, the one that took longer than half a minute to draw, will be his last.

"Any anxiety I feel is more to do with success and failure."

Although the heart is a relatively small muscle and doesn't consume an enormous amount of precious oxygen, an elevated heart-rate is the enemy of a diver. Trubridge has a relatively high resting rate (about 55 beats per minute), but when he dives it will be around 30.

"If it's higher than that it usually means there's something else going on, and that can be hard to stop."

In that respect, diving can be the ultimate mind trick: success, which you desperately want, is easier to achieve by putting all thoughts of success to one side.

Autopilot is a phrase Trubridge likes to use, and at this point of the dive, with negative buoyancy and the pressure acting like an underwater vice, it is the only state he can be in.


The tags are in reach. Trubridge will reach down and pull one free. He will then turn around, point himself to the surface and start stroking again, for the first time since he passed 23m.

At this point, "my lungs are about the size of Coke cans". The air inside him has compressed to about 11 per cent of the original volume.

The pressure causes the brain to absorb more nitrogen than usual. It brings on a light-headed feeling caused narcosis.

Sometimes known by the more dramatic term "rapture of the deep", narcosis affects all divers. Because it is an anaesthetic feeling, similar to drunkenness, some even find it pleasant. All anxiety is erased and they feel like they have become masters of all they survey.

"It can have a soporific effect. You feel woozy. You may even have hallucinations," Trubridge says.

The return

Nearly every freedive enthusiast in the world could plumb to 102m. The external pressure from the water does not make it easy, but it's certainly the easiest part.

It's getting back to the top which is tricky.

As Sir Edmund Hillary once dismissively noted when asked about the theory that George Mallory and Sandy Irvine may have summited Mt Everest some 19 years before he and Tenzing Norgay did: "I am rather inclined to think personally that maybe it is quite important, the getting down, and the complete climb of a mountain is reaching the summit and getting safely to the bottom again."

The rise to the surface can be torrid, though someone as adept as Trubridge will say it is all part of the process.

"You can feel the effects of the negative internal pressure, the constriction of the sternum and the trachea," Trubridge says.

Most of all, the body just wants to breathe. The respiratory system runs on instinct. It is silently screaming in protest. The ribcage will expand and pull the diaphragm up. That's its way of telling its human shell not just that it needs oxygen, but also that it needs to expel the carbon dioxide that has built up.

Trubridge desperately wants to feed the body what it needs and get rid of what it doesn't, but first he must break the surface.

At 40m he is met by two safety divers, who use fins to tread water while monitoring Trubridge's form and time.

During his failed attempt at 102m in December 2014, it was these divers who propelled him safely to the surface when Trubridge indicated he had nothing left to give.

This year, they would not be needed, instead acting as two benign observers with the best seats in the house.

The surface

You'd think it would be all over wouldn't you, when your mouth finally gets to open and greedily gulp the air that will fill your tortured lungs?

But freediving protocol has one last mean trick for you: a three-step process to prove your mind has recovered sufficiently from its narcosis.

Trubridge has 15 seconds to remove his facial equipment (goggles and noseclip), make a sign to indicate he is okay, then verbally express he is okay.

When this is done, Trubridge will weakly splash about; he will celebrate; he will spend the next 10 to 15 minutes panting as his respiratory system seeks the equilibrium it was denied for those four minutes and change.

Within 36 to 48 hours, he will be fully recovered, physically at least.

Then he'll start to wonder, again.

The future

There'll be a competition in Dominica before the year is out, then the biggies, the Vertical Blue in May and AIDA freediving world champs a couple of months later.

These feed Trubridge's competitive urges but what really intrigues him is that there's a lot of space down there below 102m. Who knows how far Trubridge will go to test the depths of his limits, or the limits of his depths?

Or, as poet E .E. Cummings said, eschewing science: "For whatever we lose (like a you or a me)/ It's always ourselves we find in the sea."

William Trubridge

Born in the UK, moved to NZ aged 18 months
Age: 36
Height: 1.85m
Weight: 75kg
Personal bests:
CNF (depth, no fins): 102m
CWF (depth, monofin): 121m
FIM (depth, pulling on line): 124m
DNF (distance, no fins): 186m
DYN (distance, monofin): 237m
STA (stationary bereath hold): 7m 29s
Trubridge has held 15 world records across the disciplines