Image by Daan Verhoeven.
William Trubridge needs no introduction in the freediving community. Born in 1980, he learned to swim at two and could freedive to 15 metres by the age of eight, though serious training didn't begin until 2003. In the years since, he has broken 18 freediving world records, many of them his own. In 2010 he became the first person to descend below 100 metres unassisted in the constant weight no-fins discipline (CNF), a pursuit documented in the film Breathe. He extended that record to 102 metres in 2016.
William is the founder of Vertical Blue, the freediving school and annual competition held at Dean's Blue Hole in the Bahamas, where he continues to teach and compete.
William shared some of his training tips with us, the kind that have helped freedivers from beginner to expert level advance their performance. As always: learn and apply these with a certified freediving instructor, and never dive or train alone. Freediving is a buddy sport.
Beginner: the common cold
When you have a viral upper respiratory infection, a common cold, diving is off the table. Mucous in the sinuses and nasopharynx makes equalising difficult or impossible, and forcing it risks a reverse block or a middle ear infection. Even pool training can work against you here: the stress it puts on the body, and the small pressure changes between the surface and just a metre of depth, can make the infection worse.
The better move is an enforced break from training, aside from maybe some gentle yoga to keep the body loose. Let your body recover with rest and a diet that supports the immune system: more fruit and vegetables, especially garlic and ginger, and less dairy and meat.
Intermediate: the protein myth
It's a common assumption that freedivers training hard need large amounts of protein. Protein is the building material for our cells, so more training should mean more protein, right? Some freedivers also worry that the CO2 generated by breath-holding causes acidosis that breaks down muscle, pushing them toward whey supplements and protein bars after every session.
In practice, the recommended daily intake of around 0.8g of protein per kilogram of bodyweight is generous, even for endurance athletes, and most people meet it comfortably through a balanced diet of grains, legumes and vegetables. The body needs comparatively little protein, and any real surplus gets broken down into uric acid and ammonia, adding to the body's acid load rather than easing it.
After a dive, the body tends to want alkaline-forming foods, ones like fruit and vegetables that leave an alkaline residue once metabolised, as opposed to acid-forming foods like meat, dairy and grains. Loading up on animal protein straight after training can add extra load to a system that's already working to recover. It's worth experimenting with cutting back on post-dive protein and leaning on whole, plant-based foods instead: some freedivers find they need fewer naps and hold their training weight more easily as a result. Grains and vegetables carry plenty of protein, and a varied diet across them will cover your amino acid needs without supplementation. As with any dietary change, what works varies person to person, so introduce it gradually and check in with a nutrition professional if you have specific health considerations.
Intermediate: training the dive reflex
Here's a short exercise for anyone familiar with the mammalian dive reflex, the body's automatic response to breath-holding and cold-water immersion that slows the heart rate and redirects blood toward the vital organs.
Imagine walking through a forest at night. A sudden crash in the bushes sends adrenaline through your veins, and in a split second your body chooses to stand your ground. A piglet bursts out and runs past. You relax.
More noises follow from a different direction. Your heart races again. This time it's a pair of chickens.
After a run of noises that all turn out to be farmyard animals, an axe-wielding figure suddenly appears in front of you. How does your body respond now?
The fight or flight response exists to supply what's needed for a genuine threat: adrenaline and other stress hormones. A few questions worth sitting with:
- What happens if the threatening stimulus is holding your breath? Which reflex gets triggered?
- When that stimulus repeats, several breath holds one after another, what happens to the strength of the reflex each time?
- What does that tell you about the best way to prepare for a maximum attempt, whether a breath hold or a dive?
This is one of the concepts explored in Vertical Blue's advanced classes, where a fuller case is made for how best to prepare the body and mind for a deep dive.
Expert: seamless swim caps
It sounds like a small detail, but for anyone training in a one-piece, triathlon-style wetsuit, a swim cap makes a real difference to surface drag. Silicon caps outperform latex, and a seamless cap means fewer folds where water can get trapped and create turbulence.
Pull the cap down firmly over your brows and the back of your head so it smooths out the surface and clears any trapped air. You can work out the last of the air by tipping your head back underwater and pressing evenly on the cap with your hands. Air left inside can vibrate as you swim, or gradually work the cap loose.
Even without the hydrodynamic benefit, swim caps help protect your ears, particularly in colder water, by reducing water circulation into the ear canal.
Image by Daan Verhoeven
Expert: resistance depth training
Pool training allows for 50m or 100m repeats all day. Depth training doesn't work the same way: one deep dive to 70m or more, followed by anything past 40 to 50m, puts you at risk of decompression sickness. There's no reliable formula for a nitrogen-safe depth training profile, since the variables involved are too many.
If you want to simulate a deeper dive without that risk, there's a simple way to add resistance: wear an old long-sleeve shirt or sweater over your wetsuit, cuffs fastened with rubber bands if needed. The billowing movement and added drag can turn a 30m dive into something closer to the effort of a 45m one. Training this way builds stroke power, so that diving without the extra layer starts to feel effortless by comparison.
This approach beats strapping on extra weight, which makes the descent easier and changes the body's inertia, or using a bungee, which carries its own risk at depth. If a shirt alone isn't enough resistance, add a wooly hat, or even a pair of jeans.
Image by Daan Verhoeven
In summary
William Trubridge has spent more than two decades pushing the limits of what the human body can do on a single breath, and he's generous with what he's learned along the way. These tips span beginner to expert level, but the fundamentals underneath them (rest, patience, and training with a buddy) apply at every stage.
For more from William, or to learn to freedive with him, visit williamtrubridge.com or verticalblue.net.
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