Wim Hof Breathing and the Water Rule: Why You Never Do It in a Pool

In short: Wim Hof breathing involves rounds of deep, fast breaths followed by a long breath hold. On dry land, it can be an intense experiment; in water, it can be deadly. Fast breathing lowers carbon dioxide, the signal that tells you to breathe, so oxygen can fall dangerously low before you feel the need for air. The Wim Hof Method’s own safety page says never practise in or near water, and drownings have been reported. The science is still early. Breathe on dry land, keep the cold plunge as a separate step, and keep any float simply for lying still.

Maybe you have tried a few rounds of Wim Hof breathing from a YouTube video and loved that tingling, wide-awake feeling. Or maybe you have seen someone breathe hard, slide into an ice bath or a pool, then hold their breath “for the gains”. There is one rule here that matters more than any technique. This is why it exists, what the research actually shows, and how to keep breathwork, cold plunge and float as three separate, safer practices.

Part of the Ōmni Recovery Library · Recovery by Breath · Ōmni Evidence Scale: Early evidence

For the cold itself, read our ice bath and Wim Hof guide; for practising the technique on a mat, see our breathwork guide. This piece zooms in on one specific question: the breath and the water.

Where it comes from, and how people do it

Wim Hof, the Dutch “Iceman”, built his method around three pillars: breathing, cold exposure and commitment. The breathing part, often compared with the Tibetan inner-heat practice of tummo, usually looks like this: around 30 to 40 deep, quick breaths, then an exhale followed by a hold with empty lungs for as long as feels comfortable, then one deep recovery breath held for about 15 seconds. Repeat for three or four rounds, and you are done.

It can feel remarkable. Your hands and lips may tingle, your head feels light, and the breath hold after the fast breathing can stretch to a minute or two with surprising ease. That sense of ease is exactly where the danger begins.

What fast breathing does to your blood

The urge to breathe mostly does not come from running out of oxygen. Your brain is watching carbon dioxide (CO₂): as it rises, you get the strong feeling of “I need air” long before oxygen would normally fall dangerously low.

Fast, deep breathing (hyperventilation) blows a large amount of CO₂ out of your blood. It adds very little extra oxygen, because your blood is already nearly full. So you begin the breath hold with the alarm turned down, while oxygen continues to fall as usual. If oxygen drops below the level your brain needs before that alarm returns, you can simply switch off. No struggle, no panic, often no warning at all. This is called shallow water blackout or, more precisely, hypoxic blackout, and it can happen in any depth of water.

This is not just theory. In the 2014 Radboud study of Wim Hof’s method, trained men’s oxygen saturation typically dropped to around 50% for a short moment during each breath hold (at rest, a healthy person sits at 95% or more). In a 2022 follow-up by the same team, only the version of the exercise with long breath holds produced these deep drops in oxygen. On a mat, a blackout usually passes within seconds. Under water, nobody may notice.

The water rule, and why it exists

The Wim Hof Method’s own safety page is unusually clear: never attempt the breathing exercises before or during diving, driving, swimming or taking a bath, or anywhere passing out could cause injury; the simplest option, it says, is to sit on a couch or the floor. The same page says not to practise the method while pregnant or with a condition such as epilepsy.

That rule exists because people have died. In 2016, the Amsterdam newspaper Het Parool reported at least three deaths among people combining the breathing with water. Journalist Scott Carney, a former practitioner turned critic, told Live Science in 2024 he had linked 31 deaths to the method, mostly drownings, though none confirmed in court. In July 2024 a California court cleared Wim Hof in the case of a 17-year-old who drowned in a pool, finding no proof that she was doing the breathing exercises at the time. So the exact numbers are disputed. The mechanism is not.

A 2015 CDC report reviewed 16 cases of “dangerous underwater breath-holding behaviours” in New York State, including intentional hyperventilation: four people died. All but one of the incidents happened in a pool, and more than half happened with other swimmers present. A blackout under water is silent: having people nearby is not the same as being actively watched. Lifesaving bodies such as the Royal Life Saving Society UK warn against hyperventilating before breath-holding in water.

Cold water adds two more risks. In the first seconds of a cold plunge, the cold shock response can trigger an involuntary gasp; gasp with your face under water and you can inhale water. And when your face is in cold water, the diving reflex tries to slow the heart while cold shock pushes it faster. Researchers Shattock and Tipton called this “autonomic conflict” and proposed it as a trigger for abnormal heart rhythms in people at risk. Professor Mike Tipton told Live Science that hyperventilating and then plunging your head into cold water is “about the most dangerous thing you can do when you go into cold water”.

The plain list:

• No Wim Hof breathing or breath holds in or near water. That means pools, the sea, the bath, the shower, a cold plunge and a float pool.
• Not right before getting in, either. Do your breathing on dry land at a different time, not as a “warm-up” on the edge of the plunge.
• Not while driving or riding a motorbike, or anywhere a sudden faint could hurt you. Sit or lie down.
• In cold water, breathe slow and long. Keep your face out and let each exhale be longer than the inhale until the gasp passes.

What the science says about the breathing itself

What has been shown. The best-known study is Kox and colleagues, 2014, in PNAS. Twelve healthy young men trained for 10 days in breathing, meditation and cold; twelve did not. All were then injected with a small dose of bacterial endotoxin, which briefly causes flu-like symptoms. The trained men showed a sharp rise in adrenaline, more of the anti-inflammatory messenger IL-10, fewer inflammatory signals and milder symptoms.

Zwaag and colleagues (2022, Psychosomatic Medicine) then pulled the bundle apart. In 48 healthy men, the breathing exercise on its own dampened inflammatory signals after endotoxin, cold training on its own did not change them overall, and breathing plus cold worked best. Two details are worth noticing. The adrenaline rise did not depend on long breath holds: the version without them produced the same initial surge. And the authors wrote that the breath-hold version “may nevertheless be less preferable from a safety perspective”.

What has not been shown. A 2024 systematic review (Almahayni and Hammond) found only eight trials, with participants about 86% male, and rated their quality very low. Anti-inflammatory findings looked promising; results for exercise performance and mood were mixed. Nothing so far shows that the breathing “boosts immunity” in daily life or treats any illness. And when Stanford researchers compared three five-minute daily breathing practices for a month (including cyclic hyperventilation with breath holds, a close cousin of Wim Hof breathing), the slow, exhale-focused cyclic sigh showed the clearest mood benefit.

Plausible versus proven. The adrenaline surge is real, and adrenaline is known to quiet parts of the immune response: that gives us a plausible chain. Whether practising at home makes you healthier over months has not been tested.

Ōmni Evidence Scale: Early evidence. A few small, well-run lab studies in healthy young men show a strong adrenaline response and a damped inflammatory response; reviews rate the overall quality as very low and long-term benefits are unproven. See how we rate evidence on the Ōmni Evidence Scale.

What we think at Ōmni

Wim Hof breathing is fascinating to experience on a quiet floor. We also run a cold plunge and float rooms, so water safety is something we think about every day. Our view is simple: breath, cold and float are three separate steps, and they work best that way.

• Breathing happens on dry land. If you enjoy Wim Hof rounds, do them sitting or lying down at home, and finish them completely. Our breathwork guide also includes slower, exhale-led options. If you practise Wim Hof breathing, keep it on dry land, sitting or lying down.
• The cold plunge is its own step. Ōmni’s cold plunge is a private 30-minute session at your own pace: a few short dips or one longer one. Step in slowly, keep your face out of the water, and use long, slow exhales. No breath holds, no breathing rounds in the water. Bring your own swimwear for the plunge (we do not lend it).
• The float is for lying still. In a float you lie on your back, face up, in about 25 cm of water with around 500 kg of dense, mineral-rich Epsom salt, warmed to 33–34 °C, close to skin temperature. You breathe normally and let the water carry you. It is not a place for breath holds or fast breathing.

Why float after the cold? The cold switches you on; the float gives everything space to settle in darkness and quiet. Float has been explored across hundreds of scientific studies; in a Swedish randomised pilot trial, 65 working adults who floated 12 times over seven weeks reported less stress and anxiety and better sleep than a waiting group.

Ōmni Evidence Scale: Strong evidence, for float and stress. We rate it Strong because, on top of these trials, user experience is overwhelmingly positive: in a 2025 survey of regular floaters, 92% reported relaxation and 77% less stress, echoed by thousands of reviews, Reddit threads and forums, and by athletes and public figures who float.

Ōmni Space is a quiet float centre at 16C Quốc Hương, Thảo Điền, from the team behind Float Vietnam, the country’s pioneer float centre since 2017. A single float costs 1,500,000 VND for 60 minutes or 2,000,000 VND for 90 minutes; the couple room adds 700,000 VND for the second person. The cold plunge and our private infrared and red-light sauna each cost 450,000 VND on their own, or 200,000 VND added to a float. Open 9:00–21:00 daily; last float 20:00; walk-ins until 18:00.

A simple day, with everything in its place: slow breathing at home, a cold plunge with long exhales, then a float. For heat and cold together, see our contrast therapy guide.

Float PlanRunning on empty?Take the one-minute Float Plan quiz: tell us how you feel and what you need, and get a simple plan for your first session.Make my Float Plan

FAQ

Can I do Wim Hof breathing in a pool, a bath or an ice bath?

No. Fast breathing followed by a breath hold can make you black out from low oxygen without warning, and in water that can mean drowning. The Wim Hof Method’s own safety page says never to practise in or near water.

Why is it dangerous if I feel completely fine?

Because feeling fine is part of the problem. Fast breathing lowers carbon dioxide, the signal that makes you want to breathe, so oxygen can fall too low before you feel any strong urge for air. The blackout is usually silent, even with other people nearby.

Can I do the breathing just before a cold plunge?

We suggest not. The Wim Hof Method says never before or during swimming or a bath. Do your breathing on dry land at another time, then enter the plunge slowly with your face out and long, slow exhales.

Does Wim Hof breathing boost your immune system?

That has not been shown. Small lab studies in healthy young men found a strong adrenaline rise and a damped inflammatory response to an injected toxin. We rate this Early evidence; long-term health effects are unproven.

Can I do breathwork during a float?

Gentle, slow breathing, yes: many people simply let the breath settle on its own. Fast breathing rounds and breath holds, no. A float is for lying face up and breathing normally.

Written by the team at Ōmni Space – Float Saigon in Thảo Điền, which runs a cold plunge, an infrared and red-light sauna and float rooms. General information, not medical advice; sources checked on 30 October 2026.

Sources

1. Kox M, van Eijk LT, Zwaag J, et al. (2014). Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. PNAS 111(20): 7379–7384. doi:10.1073/pnas.1322174111
2. Zwaag J, Naaktgeboren R, van Herwaarden AE, Pickkers P, Kox M (2022). The effects of cold exposure training and a breathing exercise on the inflammatory response in humans: a pilot study. Psychosomatic Medicine 84(4): 457–467. doi:10.1097/PSY.0000000000001065
3. Almahayni O, Hammond L (2024). Does the Wim Hof Method have a beneficial impact on physiological and psychological outcomes in healthy and non-healthy participants? A systematic review. PLOS ONE 19(3): e0286933. doi:10.1371/journal.pone.0286933
4. Balban MY, Neri E, Kogon MM, et al. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine 4(1): 100895. doi:10.1016/j.xcrm.2022.100895
5. Wim Hof Method. Safety warnings (checked 30 October 2026).
6. Centers for Disease Control and Prevention (2015). Fatal and nonfatal drowning outcomes related to dangerous underwater breath-holding behaviors — New York State, 1988–2011. MMWR 64(19): 518–521.
7. Royal Life Saving Society UK. Shallow water blackout, hyperventilation and breath holding (GS005).
8. Pester P (5 April 2024). ‘Gambling with your life’: experts weigh in on dangers of the Wim Hof method. Live Science.
9. DutchNews.nl (3 July 2024). “Iceman” Wim Hof cleared of causing death of American teenager.
10. Shattock MJ, Tipton MJ (2012). “Autonomic conflict”: a different way to die during cold water immersion? The Journal of Physiology 590(14): 3219–3230. doi:10.1113/jphysiol.2012.229864
11. Kjellgren A, Westman J (2014). Beneficial effects of treatment with sensory isolation in flotation-tank as a preventive health-care intervention: a randomized controlled pilot trial. BMC Complementary and Alternative Medicine 14: 417.
12. Hilpert K, Chis Ster I (2025). Experiences and perceptions of regular floatation-REST users: results from an online survey. Journal of Clinical Images and Medical Case Reports 6(5): 3600.