Breath: Have the Diving Women of Jeju Island Been Using World Record Holder (Iceman) Wim Hof’s Cold Exposure Method for the Last 1500 Years?

In the winter of 2015, I first saw Wim Hof, the incredible Iceman, on Hof is known for an amazing array of feats, many of which involve withstanding extreme arctic temperatures while experiencing little or no negative effects on his body. Hof has beat 20 Guinness World Records, including submerging himself in ice longer than any other human. He has climbed Everest in nothing but shorts and has run a marathon above the arctic circle in the same uniform. Hof points out he is not the first human to pull off such feats. Others, he says, have been doing the same thing around the world, but it was he who first went to science. Against their expectations,  scientists in the Netherlands discovered that Hof was correct about the efficacy of his method. He has shown that he is able to teach others to withstand extreme conditions of cold just as he has taught himself to do.

Last year, I started making connections between Hof’s iceman training methodology and the practice of non-assisted diving native to Jeju Island. Jeju is located about 70 kilometers off the southern coast of the Korean peninsula.  It is the largest of South Korea’s islands. I’ve spent eleven years on Jeju, six of which I worked primarily as an English instructor and the last five documenting the waning practice of shamanism, particularly focusing on oral histories of practitioners and myth collecting. I have an independently produced, full-length documentary on the subject set for release this September (2016). I have spent many long hours interviewing and chatting informally with Jeju Island’s famed breath-hold divers, called haenyo in Korean, literally ‘sea-woman’, but often translated as ‘woman diver’ in English.

A haenyo emerges from a dive.

Jeju Island’s haenyo, while once considered low-caste, have now been elevated in status, becoming a primary symbol of the island’s culture. Each seaside village has a community of haenyo that work more or less autonomously within the village. Each group of divers, largely made up of elderly women, control a territory in which they employ expert breath-hold diving skills to harvest abalone, turban shells, sea urchins and other delicacies from the sea floor. The work entails a gruesome amount of difficult labor. Haenyo dive up to four hours in the summer months and one to two hours in the winter season. During such dives, they descend to the ocean floor up to 60 times an hour, pick up or cut sea life from the seabed and then return to the surface. This is just the primary harvesting. Processing their catch is a whole other ordeal. I’ve known divers that carried 70 kilos on their back at advanced ages. Needless to say, withstanding the cold and keeping enough oxygen in the body for long periods underwater, is a crucial part of their work. South Korea is a country that can see brutal winters. Jeju Island is no exception. Waters are generally around 10-12 degrees celsius in January and February.

It’s hard to say exactly when I started thinking about Wim Hof’s methods for cold endurance and breath-hold diving in relation to the haenyo, but I believe it stems from a particular trip I took with friends to Jongdal Village located in Gujwa County on the north-eastern coast. On that day, a few researcher friends and I had been invited to witness a dive by a haenyo we had met the week prior at a syncretic shamanic ceremony for the sea god, which was performed by a Buddhist monk. On that day in February, the four of us boarded a boat which carried around twenty divers out to sea for a breath-hold diving session. Haenyo dive up to twenty meters without the use of any assistance. They generally go out to sea with a weight belt, a trowel and styrofoam float which they use to rest on. For the last thirty years or so divers have used modern wetsuits. Before then, they dove dressed in cotton, even in winter, a detail which is important.

On that day in Jongdal, we accompanied the divers out to sea in a five ton boat and returned to shore after the women all jumped off and plunged into the water. The boat captain in charge of dropping the women off and later retrieving them, told us to meet back at the boat in three hours. For about an hour my friends and I combed the waters edge and listened calmly to the sounds of the divers at work some thirty yards off the shoreline. We heard the women singing while resting and we heard the famous ‘sumbisori‘, a curious whistling sound that divers produce when they break the surface of the water. It’s a little difficult to describe the sound, but it is something like a two-toned ‘Oi-Oi’ (Oi like in punk music) or ‘Ew-eee’ (Ew like yuck), where the second syllable shoots high an octave.

Hailing the captain.


I recall discussing that day in Jongdal how amazing it was that the women, many of them elderly, could maintain vigorous activity in such frigid water. At the time, I wouldn’t have guessed that ‘sumbisori’ might have something to do with it. I later realized, while experimenting with making whistling sounds myself and blowing sounds out of my mouth, that producing vocalizations slows down exhalation. You breath slower when whistling or making noise as you are constricting your vocal chords and decreasing the area of the opening of the mouth and probably the throat. I’m no expert, but a simple test of breathing out without vocalization as hard as I could vs. whistling or making other sound was obviously a case for fast exhalation vs. slower exhalation. This struck me as odd because I had read in the literature many times and heard it stated as common knowledge that ‘sumbisori‘ was a technique for emptying the lungs quickly. I realized through my test that this couldn’t be the case. ‘Sumbisori‘, which literally means breath sound, slowed down exhalation.

Listen to ‘sumbisori’ in this youtube video:

(Note on ‘sumbisori‘: ‘Sumbisori‘ already has a host of common explanations and theories explaining its purpose. On Jeju Island, you can regularly hear about it functioning as a sort of beacon device for divers, who can identify one another through the sound. This helps the divers keep track of each others’ position and to signal one another if anything is amiss. I tend to think this is correct, but there is much more to it. According to Joo-Young Lee, divers claim that it helps ‘protect their lungs’ (citation/link to paper, 2014). Shamans on the island have attributed the whistling sound to letting the gods know the divers’ locations in the ocean lest they need divine assistance. The function of the Valsalva maneuver has also been postulated and no doubt, the breathing methods including the ‘sumbisori‘ are part of a surfacing protocol, a variation that breath-hold divers use worldwide.)

Since ‘sumbisori‘ slows downs exhalation, not increases it, and the haenyo are able to withstand extreme cold for extended periods of time, I can’t help but draw parallels to  Wim Hof. Hof’s method relies on three components that serve to turn the practitioner into a ‘superhuman’ who can hold their breath for extended periods of time, withstand the cold and raise ones resting metabolism at will by consciously accessing the sympathetic nervous system.

From Hof’s free online course book

The three components of the WHM (Wim Hof Method) are as follows:

  • Breathing exercises
  • Training of mindset/concentration
  • Gradual exposure to the cold

Let’s look at breathing exercises for now. I will comment on exposure to cold and mindset/concentration later, drawing parallels to the haenyo’s diving practices.

Hof’s manual reads:

Regulated by the autonomic nervous system, inhaling oxygen is an unconscious process. Fortunately it’s an unconscious praxis, otherwise we simply wouldn’t have a break, as we’d have to deal with it incessantly. The amount of oxygen that we inhale through our breathing influences the amount of energy that is released into our body cells. On a molecular level, this progresses via various chemical and physiological processes. Breathing is the easiest and most instrumental part of the autonomic nervous system to control and navigate. In fact, the way you breathe strongly affects the chemical and physiological activities in your body. Throughout the years, Wim Hof has developed special breathing exertions that keep his body in optimal condition and in complete control in the most extreme conditions. The breathing technique is first and foremost premised on inhaling deeply and exhaling without any use of force!

He goes on to say (in Hof’s own words):

Hof: “By not breathing out entirely,  you come to a point where a residual of air remains in the lungs. After doing this thirty times, you exhale again without any use of force. This time though, you don’t immediately inhale again, but wait with inhaling until you sense your body needs new oxygen. After this, the whole process starts again. While you start to (feel) sensations of lightness, laxity and tingling, these rounds are repeated a number of times”.


The breathing process which Hof has perfected and teaches to his students, a session of which you can witness in the Vice documentary linked at the top of this post (andHERE ), has the goal of ‘controlled hyperventilation’, something divers and swimmers use to increase the amount of time which they can hold oxygen in their bodies. While ‘sumbisori’ no doubt functions to help haenyo identify each other at sea, the limited exhaling it allows suggests that the women are pretty much using (purposely or through happenstance) some variation of Hof’s iceman method. It’s controlled hyperventilated breathing combined with cold exposure.

From Hae Nyo, The Diving Women of Korea (Suk Ki Hong, Yonsei University College of Medicine. Paper presented in 1965 as part of the Tokyo Symposium on the Physiology of Breath-hold Diving pg. 108 PDF)

Screen Shot 2016-07-05 at 1.24.16 PM

The other factors involved in the matter of the ‘sumbisori‘ whistling sound as commented on by Suk Ki Hong in his 1965 paper, apart from controlling excessive hyperventilation, could be inducing a certain amount of hyperventilation, but just enough to achieve the benefits laid out by Hof, benefits such as increased metabolism, ability to load the body with higher amounts of oxygen, production of epinephrine and higher focus. Over time, no doubt centuries, the haenyo have perfected a diving pattern that minimizes risks and increases physiological benefits.

From Surfer Magazine:

According to Hof’s method, we can tap into special parts of our brains, change our pH levels, and release adrenaline at will by utilizing his controlled hyperventilation technique. The results of his breathing method, followed by submergence in a cold shower or an ice bath, enable the body to perform on a higher physiological plane and bring focus to the mind. 

The Wim Hof breathing method:



Cold Exposure

Here is Joo-Young Lee and Hyo Hyun Lee’s (Seoul National University, College of Human Ecology 2014) review of the literature on acclimatization/deacclimatization to cold in haenyo breath-hold diving. For those who want to dig deeper:


From their paper:

In those days haenyeos (before Korean haenyo wore modern wetsuits) were known as being more tolerable to cold water than Japanese female ama, which is related to differences in wetsuits, cold adaptation, body temperature

sea water temperatures and work practices between Korea and Japan. Sea water temperatures in winter were lower in Korea than in Japan: on average of 3.4°C around the middle area of Korea and 13.6°C at the Jeju island, but on average over 14.0°C around both Tokyo and Fukuoka in winter (, 2014). Furthermore, haenyeos dived even in the middle of winter wearing only thin cotton bathing suits called ‘so- jung-ee’ (literally translated as ‘something precious’).


When sufficiently exposed to cold, all humans adapt to cold through increased metabolic rates and with an attendant increase in peripheral tempera- ture. Kang et al. (1963) reported that haenyeos’ basal metabolic rate (BMR) during the winter months, when they were diving in very cold water, was significantly elevated above values observed during warmer months. Haenyeos increased their BMR by ~35% during the winter, while BMR of non-divers was maintained at a normal level throughout the year (Kang et al., 1963) (Fig. 5). Daily urine samples indicated that excretion of nitrogen was the same in haenyeos and in control subjects. For this reason, Hong and his colleagues sug- gested that the increase in BMR in haenyeos in the cold season is a manifestation of a metabolic acclimatization to cold stress and cannot be caused by differences in diet. The 35% increase in BMR could be due to an increased utilization of thyroid hormones (Hong, 1973) and to a slight increase in sensitivity to norepinephrine (Kang et al., 1970). Thyroid hormones and norepi- nephrine both stimulate metabolism.


Hof’s cold exposure method aims to do exactly this, manipulate the release of epinephrine in the body. While the above study only postulates this, scientists studying Hof have proved it.

1 IMG_9221_01
Haenyo sing and pray at a syncretic Buddhist ritual performed for the Sea God.


So, let’s return to the three components of Wim Hof’s method. Once again, they are:

  • Breathing exercises
  • Training of mindset/concentration
  • Gradual exposure to the cold

We have covered breathing exercise and sumbisori’s similarity to Hof’s method. ‘Sumbisori‘ involves whistling to limit the speed and volume in which breath exits the body, mirroring the process of Hof’s technique.

Gradual exposure to cold is also evident. Divers, over the course of adolescence, are indeed graduated into full-on, breath-hold diving. One would assume that their experience with cold exposure, in the era before the haenyo wore modern wetsuits, was also gradual.

I have left out Training of mindset/ concentration. I will say a bit about this now.

I have a notion that the haenyo‘s lifestyle, the religious/ cultural aspects and physical aspects do indeed encourage mindset and concentration training.  The many acts that haenyo perform such as sorting and processing their catch are repetitive and would tend to bring them into flow states which are a higher order of concentration. Also, shamanic music, which I have documented in my upcoming film, is of the sort which is recognized to encourage trance states in the listener. Buddhist chanting, which many of the divers practice, is also a known trance state inducer. There is also building evidence of late that simply being in proximity to the ocean can increase one’s concentration. Check out Wallce J. Nichol’s Book, Blue Mind: The Surprising Science that Shows How Being Near, In, On, or Under Water Can Make You Happier, Healthier, More Connected, and Better at What You Do. Amazon.

An article on Nichol’s main findings: Huffpost

Lastly, I would theorize that the ‘sumbisori‘ itself, along with natural ocean sounds of lapping waves and underwater reverberations, serve to induce altered states, heightened concentration and relaxation. If you witness a group of divers performing their work, you will observe that the ‘sumbisori’ creates a sort of field of sound in the ocean which envelops the divers. The ‘sumbisori’ of nearby divers surrounds other divers. Divers are alone enough to slip into flow states, concentrating on their own work, as they position themselves some meters away from other divers, but are coddled in a sonic blanket of reminders that they are not alone. The sound is a pleasant one, not something that would break concentration.

Women divers in Jeju often dive apart, but can still hear one another’s ‘sumbisori’.

Video of syncretic Buddhist chanting. Mid-winter rite for the Sea-God. (Below)

I am considering to start with interviews of the divers and ask them to teach me the ‘sumbisori’ techniques so I could compare them to Hof’s method. This is something I will begin to undertake this summer. Over the years, I have met many divers and still keep in touch with many of them who live at different locals around Jeju Island. I’ll be updating here with what I learn from the haenyo I know.

I actually made use of Hof’s breathing method last winter when I didn’t have hot water for my shower. Due to financial issues, I was unable to pay my water bill for most of 2015. I noticed when I did the controlled hyperventilation breathing before standing under the freezing stream of water, that it was a much more endurable experience than without the breathing. I have also experienced acclimatization to cold in periods of my life where I spent the majority of my waking hours outside in freezing or near-freezing conditions, nothing on the order of what Hof and the haenyo have done, of course.

Vim Hof’s method entails using controlled breathing, cold exposure and concentration to change the body’s physiology. These changes allow the practitioner to hold their breath for longer, resist cold temperatures and function similarly in freezing conditions as one does in warm temperatures, raise resting metabolism, increase immune responses and overall endurance when performing intense, physical actions. Jeju Island’s haenyo have quite possibly been doing all this for at least 1500 years. Perhaps, their own version of the WHM warrants further investigation before their time comes to and end.

Are the haenyo and Wim Hof really using versions of the same method?

It is possible, of course, that the three elements involved in the WHM- breathing, cold exposure and concentration just happen to converge in the haenyos’ diving practice. ‘Sumbisori’ has been reported amongst the Ama divers in Japan and also in other parts of the world where breath-hold diving exists. Also, some western breath-hold divers have reported incorporating whistling or other sounds into their breathing techniques. The ‘sumbisori’ obviously provides plenty of functionality apart from aiding in resistance to cold. It is pretty interesting though to note that Tummo meditation technique in Nepal and Hof’s technique both involve similar breathing practices that affect the body’s metabolic processes.

Jeju Island’s haenyo are among the few instances in the world where long-term cold adaptation has been available for study. I’m curious to discover if haenyo (diving before the advent of the modern wetsuit) were aware of employing concentration/ breathing techniques to help them endure the cold. A footnote from Suk Ki Hong’s 1965 paper ‘Heat Exchange and Basal Metabolism of Ama’ peaks my interest. While all women divers in Jeju showed a 35% increase in resting metabolic rate during the winter, even while not diving (Hof has shown an astounding 300% increase without raising his heart rate ), there were two Ama (Ama is the Japanese word for haenyo) omitted from the study who had resting metabolic rates at 120%. I wonder if these two divers were in possession of some of Hof’s super abilities.

Screen Shot 2016-07-07 at 4.02.45 PM

In the present era, haenyo have very much the same body chemistry as normal Jeju Islanders due to their use of modern wetsuits. Older divers though, experienced diving in the era of cotton suits and may be able to offer observations on their past experiences of cold water diving.


About  the Iceman Wim Hof and his methods:

Wim Hof Wikipedia

Wim Hof Method Free Instruction Guide PDF

Wim Hof’s website

Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. 2014 paper vindicating Hof’s claim that humans can voluntarily activate the sympathetic nervous system. Authors names available in link.

Criticism of Vim Hof/ Blog of Vim Hof detractor Pepijn van Erp

Wim Hof on Joe Rogan’s podcast

Wim Hof on Tim Ferriss’s podcast If you are interest in cold exposure there is a ton of stuff on Ferriss’s website, search in the search bar. He writes about his experiments with cold extensively in the Four Hour Body. Amazon.

Tim Ferriss on ice-baths Youtube

1965 Conference material on the physiology of breath-hold diving:

Rubicon Foundation: Physiology of Breath-Hold Diving and the Ama of Japan. Link to papers presented at a symposium held in Tokyo in 1965 with a collection of papers on the physiology of breath-hold diving. Downloadable pdf link at bottom of page.

Joo-Young Lee and Hyo Hyun Lee 2014 paper:

Korean Women Divers ‘Haenyeo’: Bathing Suits and Acclimatization to Cold Joo-Young Lee and Hyo Hyun Lee pdf

Video installation on the haenyo including ‘sumbisori’:

Promo Video of SeaWomen by Mikhail Karikis Beautiful video installation piece on heanyo including sumbisori sounds and haenyo work songs.

Tummo Meditation breathing:

Tummo meditation youtube Tumo meditation accomplishes similar goals to Vim Hof’s methodology and has also been scientifically vindicated. The meditation is said to have been developed in Tibet so monks who spent time in cold caves could warm themselves.

7 Comments Add yours

  1. brilliant article Joe, well researched & neatly presented. i was particularly taken by the discovery that the sea increases concentration. this makes sense when you think of the countless poems, prose & music inspired by the sea: The Old Man & the Sea; Hart Crane’s Voyages series & much of Wallace Stevens poetry, Debussy’s La Mer; & much of it probably having been created beside the sea or at least the work’s inception. i too have found that when i go sit beside the sea in Ongpo i always come away with something. makes me happy that.

    Liked by 1 person

    1. joeyrositano says:

      Thanks for the read, Daniel. About the sea, funny how so much research seems to confirm things we already know.


      1. my pleasure i only wish you had time to write more. there are many wonderful blogs, but not as many as you’d expect & your research is original & thorough, & a rare gem in a quagmire of uncertain minds trying to be certain of something.
        i couldn’t agree more on our finding things we already know. i always used to say back in my university days, when i coupled two seemingly remote authors or ideas that its like ticking boxes. not a great analogy but it summed up the few criteria that essentially exist between acutely human or natural things.


  2. Joe says:

    What do you think about the concern of blackouts underwater? I am currently performing Wim’s 10 week program and am also a trained freediver. Wim’s method aims to decrease CO2 as much as possible to attain high levels of O2. Low CO2 is very dangerous while free diving, even though it increases breath hold times. If CO2 levels are low, your urge to breath is reduced, and can lead to blackouts and subsequently drowning. I will not do Wim’s method before diving, but I wonder how safe these women are related to blackouts.


    1. joeyrositano says:

      Hi Joe, thanks so much for the comment. I’m sorry I didn’t catch it earlier. I don’t believe the women divers on Jeju Island have this issue as their methodology seems to not be as intensive as WHM before entering the water. I believe that they must be using a modified version of a similar method that has been tailored over the years. I have some updates coming and have been filming and interviewing the divers directly on their methodology. It is a bit hard-going because it seems that in each community there are divers that are using a traditional method and many others who, because of the advent of modern diving suits perhaps, that exercise no particular formal breathing method. In the last weeks I’ve been having divers show me as best they can their method, but many learned when they were really young, around 5-10 years old and can’t remember their exact method they were taught. For sure, there are a number of women in each community who can stay underwater and resist the cold better than others. Those women are using a more formal breathing method, including whistling and hyperventilation like Hof, but certainly not as extreme (Don’t try it!). These individuals are vastly in the minority and I suspect that they are the ‘superwomen’ that the Japanese researchers discovered from years past. I’ll be updating soon. The women divers’ blood-work certainly shows they are doing something similar to Hof, the thing is to find the individuals in the modern era who are still at it. Will report more soon!

      The divers here certainly do have blackouts and other accidents, sometimes it is fatal. Divers perish every year. I’m not sure about the causality of such accidents.


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