in: Fitness, Health & Fitness, Podcast

• Last updated: July 2, 2023

Podcast #141: The Science of Freediving and Breatholding

When I was researching my post on how to hold your breath a few weeks ago, I came across a book called Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves by James Nestor. In it, Nestor highlights the art of freediving — a competitive endeavor in which people dive down to depths of 400 feet on just a single breath. To reach that depth and make it back to the surface, freedivers have to hold their breath for 4 minutes. Blackouts are common and people have died trying to break new records.

But besides these daredevil athletes, Nestor came across a group of renegade scientists who are using freediving to learn more about what’s going on in the ocean’s depths, particularly with dolphins and whales. By not using SCUBA or submarines, these scientists are getting a much closer look at these animals than we ever have before, which has put them on the brink of learning how to communicate with these fascinating creatures. It sounds New Agey, but it’s not.

Today on the podcast, James and I discuss what he learned about the human body and about our connection to the ocean as he followed freedivers around the world, and we end the show by talking about his own experience learning how to freedive.

Show Highlights

  • What happens to the human body when you hold your breath for a long time and dive to great depths in the ocean
  • How freediving used to be a common practice in ancient cultures
  • How to train yourself for freediving
  • The women in a remote Japanese community who have continued a tradition of freediving that stretches back 2,000 years
  • How scientists researching dolphins and whales are using freediving to further their research
  • The crazy theory that dolphins and whales communicate with holographic/sonar imagery (it’s nuts!)
  • Why there will probably never be underwater cities
  • James’ experience learning how to freedive
  • And much more!

Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves book cover James Nestor.

Deep is a fun read full of fascinating insights into the science of the human body and the drive to test its limits. If you’re interested in getting started with freediving, I definitely recommend picking up a copy. Even if you’re not interested in freediving, I think you’ll enjoy learning about all the remarkable science and research that’s being done in the oceans.

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Brett McKay: Brett McKay here and welcome to another edition of the Art of Manliness Podcast. When I was a kid, one of my heroes was Harry Houdini. He was known for a lot of his feats of escape, getting out of handcuffs and straitjackets, things like that, but he could also hold his breath for an incredibly long time because sometimes his tricks required him to be underwater for a long time. I think his record was a little over 3 minute is how long he could hold his breath. Anyways, a few weeks ago, I did some research and published an article about how to hold your breath for a really long time, inspired by Harry Houdini. In my research, I came across a book that was written by my guest today. It’s called Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves and it is by James Nestor.

In this book, James follows a group of renegade athletes and scientists who use freediving as both a competition sport, as well as a tool to do scientific research. What freediving is is you basically just take one, big breath and go down underwater at great depths, all in one breath, and get back up. In the competitive sport, some of these people are going down 300 feet on one breath and then in the research aspect, they’re using freediving to get up close and personal with whales and dolphins, just with their breath. They’re not using submarines because that spooks out the animals.

Anyways, in his research, James discovered that in a lot of ways, our body is designed to be in the water and to hold our breath for a long time because some weird stuff starts happening when we do that. Today on the podcast, we’re going to discuss the science of freediving, what happens to your body when you hold your breath for a long time, and then how scientists are using this capability to uncover some mysteries of the ocean. Really fun podcast, a lot of fascinating insights. You’re going to learn how to hold your breath for a long time, so that’s something you want to do, you’ll know how to do that the end of the podcast, so without further ado, James Nestor, Deep.

James Nestor, welcome to the show.

James Nestor: Thanks a lot.

Brett McKay: All right, so your book Deep is about this world of freediving, and we’ll get into some of these characters who are involved in this world. I didn’t know much about this before I read your book. How did you discover the world of freediving? Did you have an interest in the research, what’s going on in the oceans, or was it the oddities of the human body that led you to it? How did that happen?

James Nestor: I grew up near the ocean in illustrious Orange County down in southern California and had always spent much of my free time in the water, but all of that free time was spent at the surface, surfing or body surfing or boogie boarding when I was young, that kind of thing. A few years ago, Outside Magazine, one I write for, asked me to go cover something called the World Freediving Championship. Now this is a very weird competition in which competitors challenge one another to see how deep they can dive and come back to the surface conscious.

I’d never seen anyone freedive before, had certainly never done it myself, didn’t know anyone who did it, so I remember on the first day of the competition sitting out on this boat, I was the only journalist out there, and watching this guy take a single breath and completely disappear into the water. He didn’t return until 4 minutes later and he had just dived about 300 feet on a single breath. This completely blew my mind. I thought the competitive aspect of freediving was pretty ridiculous. People were coming up blacked out with blood on their faces. One guy came up technically dead for 2 minutes, but something about the human body being able to do this really stuck with me. One thing led to another and I ended up pursuing it for the next 2 years and writing a book about it.

Brett McKay: All right. Yeah, this sport, it’s sort of renegade. It’s sort of on the outskirts of sport because it is so dangerous.

James Nestor: It’s very dangerous and the competitive freedivers don’t seem to want to admit that it’s dangerous because if you have that kernel of doubt while you’re doing it, you won’t be able to do it. It’s a mental sport more than anything else. I was lucky enough at the competition to meet some other freedivers who took a more holistic and sane approach to freediving, who showed me this completely other side of freediving that had nothing to do with competitions. It was almost more of a yogic practice and that’s the side of freediving I focused on, but my entre into this world was through the competition. I could give you a zillion stories of just how crazy that stuff is.

Brett McKay: Yeah, and you talk a lot about those in the book. I’m curious, though, how is it that the human body is able … We’re land animals, right? How is it that people are able to hold their breath 4 minutes? Some people are up at like 20 minutes on a single breath and then go down to depths of 300, 400 feet when just the pressure just crushing down on your body, but they’re able to come back and live. What’s going on in our bodies when we hold our breath for that long and go underwater that deep?

James Nestor: This was something that just completely blew my mind and convinced me that there was something in freediving that I wanted to spend more time researching it and really exploring it. I learned about something that I’d never heard before called the mammalian dive reflex. These are a series of triggers in the human body that occur the second we put our faces in the water. The old tradition of splashing your face with cool water to get you to calm down, it’s not just psychological, it’s physiological. What happens is the second your face touches water, your heart rate’s going to lower about 30% of its normal resting rate and blood is going to start coursing in from your extremities into your chest area, into your core.

The deeper you go in water, the more pronounced these reflexes become. Freedivers have recorded heart rates as low as 7 beats per minute, which is, by far, the lowest anyone has ever recorded their heart rate. According to physiologists, a heart rate that low can’t support consciousness, yet deep in the water, it does. As the pressure mounts, every 33 feet, the pressure doubles in water and you feel this. Your chest will shrink up to about half its size at around 300 feet, but the body has all of these incredible mechanisms that only occur in water that protect us from the deep waters pressures. They’re the exact same reflexes that dolphins and whales and seals have to protect themselves from diving thousands and thousands of feet deep. We have those too, so we’re really born to do this.

Brett McKay: Yeah, you call it the Master Switch, right?

James Nestor: That’s right. Some scientists named it the Master Switch because our whole bodies, we turn from terrestrial beings to almost aquatic beings the deeper and deeper we go into the water. I know this sounds totally crazy, like some new-age dream, but this is all hard science and people have been studying this for over 50 years. Once I learned about that, it just really, the fact that I had never heard of it before and that there was so much more to learn and to research about it really convinced me that there might be an interesting book in here.

Brett McKay: Is it because we, from a literal sense, come from the water, right?

James Nestor: We don’t know exactly why. Just like with all evolution, it’s sort of a messy route to get to where we are now. Some markers indicate that that very well could be the case. The blood right now and in your veins and my veins and everyone else’s veins is about 98% similar to seawater and the amniotic fluid in which a fetus develops is about 99% seawater. Is it a coincidence? Maybe, but that seems a little too close for me. A lot of people say that we’ve developed these skills because in the past, we needed them. People have been freediving for as long as people have been recording history. Even before that, there’s evidence of freediving 20,000 years ago all over the world. It’s just recently that we stopped freediving because we no longer need to go to the seafloor to get food. We have fishing boats and nets to do that. It’s really been a part of our human evolution is being in water and being deep in the water.

Brett McKay: Are there still any group, “traditional”, I guess, cultures, that still use freediving for a practical purpose? It’s part of their livelihood?

James Nestor: Yeah. In the past, about 400, 500 years ago, the largest fishing fleet in the world was this group of Japanese women called the Ama and they just spent their lives from the time they were teenagers until they were very old harvesting urchin and abalone and fish, all those good things on the seafloor. All of the pearl divers from the past, those were all freedivers. Sponge divers in Greece, all freedivers. The Vikings were pretty good freedivers. They used to go over to enemy ships and bore holes in the ships when they weren’t looking.

As far as any of these cultures being around, most people do it recreationally now, but I was asking myself the same question about a year and a half ago. I went to Japan and actually found some of these Ama divers, the last Ama divers who actually do this for a living. One of them was 82 years old and she’d been diving every day since she was 16. She was just the biggest badass you’ve ever seen. It was great to see that they were keeping the tradition alive, at least for now, who knows how long it’ll last, and see these people that were just so intimately connected to the ocean.

Brett McKay: Yeah, and it was really interesting to see their approach compared to what you said, the competitive freedivers where they’re just crazy. These Ama were able to do phenomenal things, but they didn’t have that I don’t know if it’s a chip on their shoulder or this weird drive. They just seemed more at one with the ocean.

James Nestor: Yeah, I think that’s a really good way of putting it. The Ama, in all of their recorded history, and there’s quite a lot of it, there’s no record of them ever competing and there was no record of them ever having an accident, ever blacking out or dying from doing this. I met half a dozen Ama who had been literally diving since they were teenagers, they said every day, and they were in their 70s and 80s. This stuff can be practiced in a sane manner. They just think competitive diving is the stupidest thing of all. It would be like competitive yoga or something like seeing how far your back can bend before you break it. Their respect of the ocean and their place in the ocean really added a different element and a different layer to freediving. It was that sort of freediving, this respectful, meditative freediving that I really glommed onto and tried to explore in the book.

Brett McKay Yeah. I thought it was interesting is that you highlight, besides these freedivers and competitive freedivers, the Ama, you highlight this band of they’re really ragtag scientists. They’re independent scientists. Often, they don’t work with universities, just doing this stuff on their own, and they’re using freediving as a tool in their research. They’re exploring things like sharks, whales, and dolphins. What kind of research are these freediving scientists doing with dolphins and whales and sharks that are helping us learn new things about the ocean that we didn’t know?

James Nestor: Yeah, that’s what I thought was so cool to discover along my many travels for this book is this isn’t only a recreation, something that people did in the past and something people are doing just for their own edification. I discovered a number of people who are freediving and using this for scientific research because something else amazing happens when you’re diving. Not only does your body transform, but a paradigm shift occurs in the water. When you try to explore other oceanic animals with scuba or with submarines, and I’m sure many of your listeners have done this, most of the time, everything swims away from you. Scuba’s very loud and same with submarines and boats, but when you freedive, you’re completely silent, so you no longer become a viewer into this other world, but an active part of it. Instead of all these animals swimming away, they start surrounding you and enveloping you in their shoals and it gets very, very weird very quickly.

A few researchers were using freediving to get closer to whales and dolphins than anyone has before. Because they have such intimate access to these animals, they’re recording data that no one else has collected. That’s what I ended up focusing on, a lot of how much we’re learning about these animals and our connection to them and their language and all that through this freediving, freediving as a tool, not just as a recreation and especially not as a sport.

Brett McKay: Yeah, so the stuff coming out about dolphins and their language and whales, as well, was crazy. You read it and you’re like man, this is like Ripley’s-Believe-It-Or-Not-type stuff or things you’d see on The Learning Channel at 2:00 in the morning. This theory, one of these freediving researchers has this theory about what is going on with dolphins when they’re communicating with one another. They’re actually transmitting holographic images through … This is like Ancient Aliens stuff going on, so can you explain a little bit that theory?

James Nestor: Yeah. If it sounds insane to everyone then it sounded equally as insane to me and so we’re all in the same boat. What happened is in the 1960s, scientists were absolutely convinced that dolphins and whales were communicating, so they took them into labs. The US Navy did tons of research into dolphin communication. They’re still doing it. At one time, they apparently translated a bunch of dolphin words and sentences, were holding these stunted conversations with them. They had a lab in the Bahamas and they were holding English-immersion workshops with dolphins, all kinds.

Brett McKay: I feel bad for the lady that was the English teacher.

James Nestor: Yeah. You know what? It was fully consensual dolphin sex. We’ll leave the details in the book. I don’t really feel bad. She was the one instigating it, so she knew what she was doing. Maybe I feel bad for her now. The next morning, something like that must feel a little strange. Wow, this is so complicated, but I’m going to try to give you the CliffsNotes version here. Dolphins and whales don’t hear sounds with 2 ears, with 2 points to collect data, but with literally tens of thousands of points underneath their jaw, so they have the equivalent of tens of thousands of ears.

We know they’re viewing the world through sonographic images. This is scientifically proven, something called echolocation. They send out a click, they wait to hear all of the data from that click, how it comes back, and they form a picture in their mind from that. All of these researchers believe that they’re also able to send these sonographic images to one another. They’re already viewing the world this way. They’re probably sending the equivalent holographic sonographic images to one another.

This is not something some crazy, new-age theory. People have been studying this or trying to study it for so long, but no one’s been able to get close enough to these animals to do any real research. These freediving researchers are the first people able to get close enough to them in their wild environment to really research them. Currently right now we’ve got a team of physicists, mathematicians, coders, you name it, and they’re building the equipment. Next year, we’re going to be doing this, collecting these sonographic images and shooting them back to them, trying to have a conversation not with words and sentences, but with shapes. It’s happening, it’s real, it’s science. It’s not some flaky thing and it could be a really big deal if we don’t all die.

Brett McKay: Yeah, and it’s all because of freediving. What does mainstream universities and researchers and scientists think of these freediving? Are they welcomed in that community, they’re like no, those guys are the weird cousins at the family reunion we don’t really associate with?

James Nestor: A little of both. It’s starting to change. A few years ago, many researchers thought what these guys were doing was extremely cruel to the animals. They thought oh, the animals should be left alone, study them from a boat. What they didn’t get is it’s always the dolphin and the whale’s choice to freedive and to swim with us. At any time, they can turn around and take off and dive. When you study them, you get in the water, a boat drops you off, you get in the water, the boat takes off, and it’s just you in the water and they can either choose to come to you or choose to go away. They’re willingly having these encounters and these encounters last like 4 hours. They surround you, they orient themselves vertically. All this weird shit starts happening, so that’s one thing.

Another thing is institutional researchers can’t swim with these animals. A, they don’t know how to freedive. B, they would never be able to do that for insurance reasons. You can’t swim with a 60-foot long animal with 8-inch long teeth. No university is going to allow researcher assistants to do that, so these guys are working completely independently and they can do whatever the hell they want, which is fantastic. That’s why they’re making such fast progress right now.

Brett McKay: How do they get their funding for this stuff?

James Nestor: That’s always a tricky thing. They get a lot of their funding from donations and they’ve also gotten some funding because they’re starting to film these encounters in 360 for virtual reality because all of these headsets, if people don’t know what that is, oh, you will come Christmastime because Sony, Samsung, Facebook, they’re all releasing virtual reality headsets. They work jobs. That, to me, is what was so cool about what they were doing. They’re not doing it for money. It’s something that they’ve just already invested so much of their time and own money in doing it. They’re doing it because no one else is going to do it and they’ve got access to these animals that no one else has had before. To me, it’s incredibly exciting. I spent a few expeditions with them, saw their research, swam with dolphins and whales, and now I really get what they’re trying to do. It’s a pretty profound experience being next to this animal which could eat you in a fricking second, but instead, chooses to sit there and send you communication clicks.

Brett McKay: Yeah, we want to talk about your own experience the whales doing freediving. Bringing back to this idea that we’re somehow connected to the ocean or connected to these animals in some way, this ability to use sonar to guide yourself around the world isn’t just unique to bats or dolphins or whales. Humans can do it too.

James Nestor: Yeah, that’s right. It seems pretty abstract when you start thinking about oh, how can a dolphin and whale really see with the frequencies of sound, how can they use this echolocation? It turns out there’s a bunch of blind activists in LA that have been doing this for a decade and teaching a bunch of other blind people how to do it just the same. What they do is they use the exact same practice as dolphins and whales. They send out a click from their mouths just like a [sound] and they listen for how that click echoes off of everything around them and they form a picture from that. These guys are able to ride their bike in Sorry, I’ll start that over. These guys are able to ride their bikes in busy city streets just clicking and listening to how it goes. They camp alone in the woods. I saw this guy ride down a flight of stairs on his mountain bike. They’re able to live completely independent lives by using this echolocation, the same echolocation that dolphins and whales use.

Something really interesting is that some researchers took them, put them in an FMRI, and looked at what was happening in their brains as they were using this echolocation. They found that their visual cortexes lit up, so there was really no difference from what these guys were seeing with the frequencies of sound to what you and I and other sighted people can see with the frequencies of light. It was the same thing in their brains and they were literally able to see with their eyes closed. It really blew my mind.

Brett McKay: Crazy. You start the book off … I want to talk about this because I thought it was funny. It made me laugh. There was, or I think there still is now because it got funding again, this underwater research facility. When I read about it, it reminded me going back to when I was a kid, I remember reading these science books back in the 80s about the future would be we’d live in these underwater cities and we’d drive submarines to different locations to see grandma and it’d be awesome. Was it as awesome as these science fiction books made them out to be?

James Nestor: I don’t want to ruin that dreamy vision you have in your head, so maybe you should just plug your ears right now when I tell you the true reality of it. It’s really hard to live underwater. There’s this place called Aquarius, which is about the size of a Winnebago and it’s under about 60 feet of water in the Florida Keys. Scientists live down there for up to 30 days at a time. It was one of the strangest places I’ve ever been in my life. There are so many challenges to living underwater. There’s the pressure, there’s the fear that everything might go wrong all of a sudden and you have to bail out. There’s the bends. If these people stay in this pressurized capsule, so if they chose at any time to suddenly just freak out and go to the surface, their blood would literally boil in their veins. They had to be very slowly decompressed over a number of days in order to go back to the surface.

That was my first entre into institutional research. They’re doing very cool stuff down there. It’s really neat, but then again, I just felt so completely removed from the ocean and that connection with the ocean. You’re always in scuba, you’re always in a wetsuit, you’re behind 3 inches of steel looking out of a window. It’s a pretty big difference going from that to being freediving in a pair of swim trunks with a bunch of whales and just having these face-to-face interactions, so that seemed like a much more direct approach was to follow the more renegade line of research, which is what I did.

Brett McKay: Yeah, so no future underwater cities?

James Nestor: They tried to do that in the 60s and 70s. Cousteau had a place. It’s still off the coast of Sudan, so you can go there and you can actually live in his little underwater hut. It’s still there. It’s just traveling in Sudan right now is really sketchy. That’s why I been there, but Germany had them, Italy had them, Japan had them, US had many of them and everyone was just like okay, we’re going to colonize the ocean. Then, once everyone spent a couple days down there in this damp, humid environment, eating dried food and looking out just a window into a dark mass, everyone was like screw this. Let’s go to space. Much more and that’s what happened.

Brett McKay: That’s funny. All right. Let’s get back to this idea of direct experience with the ocean. You weren’t just writing about these guys. You actually trained to become a freediver. What was that training like and what was the culmination of that for you?

James Nestor: Yeah, the first couple assignments when I went out to see what they were doing, researching sharks and researching dolphins and whales, I was stuck on the boat the whole time. I was watching these guys from the boat in this crystal clear water, having these incredible experiences and I thought damn, that looks pretty good. I also thought if I’m going to write about this stuff, I need to experience it myself. I didn’t want to be lazy, sit behind a desk and write about it. I wanted to get in there, so I did start training for freediving.

I’ll just make something clear to the readers. This freediving, it gets lumped in with base jumping all the time. These 2 activities are so … With base jumping, you have to just off a cliff or an antenna or a bridge and each time you base jump is dangerous. Freediving, people don’t get you don’t need to go down 300 feet to do it. You can go down 10 feet or 15 feet or 5 feet or whatever depth is comfortable for you. I learned about that and I also learned that this is a mental activity. Our bodies are built to dive deep. We have all these reflexes. We’re born to do this, but getting your mind to convince yourself that you can stay underwater for 4 minutes takes a bit of time. Eventually, I was able to get there and it’s just the coolest thing I’ve ever done in my life. Since the book came out, I’ve been freediving more now than I ever have. I just think about it all the time.

Brett McKay: Oh, so you’re still doing it?

James Nestor: All the time. Yeah, this wasn’t some flighty thing where I was just like oh, I’m going to check that out and then move on to driving race cars, although that would be cool. Agents out there, I’m here. I’m ready to roll. For me, it was once I had the experience of actually feeling all of those reflexes within my own body, learning what I was capable of, learning how easy this stuff was, learning that it could be done in a very safe and respectable and meditative way, it’s just such an incredible experience. I’ll never be able to afford intergalactic travel, but this is about as close as you can get. There’s no gravity down there or you’re entirely weightless. You can do whatever you want. Animals come up to you. It’s a very magical experience and it’s something I just can’t wait to repeat. I’m going freediving in a couple weeks in Japan to do exactly that.

Brett McKay: If someone who’s listening to this, how do you get started with that? Are there schools you can go to? How do you get started with freediving?

James Nestor: The best thing to do is to take a course because they teach you about the safety, they teach you this is not some reckless, extreme thing where you push yourself to your limit and come back out of breath. It’s a meditative practice, it’s a yogic practice. You have to respect your body and your place in the ocean, so a course is the best thing. I think Performance Freediving International teaches great courses. It’s really no bullshit. They teach you about safety first and then they just take you step by step through the process.

A lot of people do this with friends, too, but it’s better to me to know the mechanics of your body and how to breathe up properly and all of the safety first. I took a course with PFI, Performance Freediving International. Really, really liked it and I know some other people that did as well.

Brett McKay: Cool. James, what are you working on next? What’s your next big project? Are you going to explore some other facet of human physiology that’s mind-blowing?

James Nestor: We’re right now working on a documentary of Deep focused on the cetacean dolphin and whale communication. What we’re hoping to do is to film these experiments as they happen. I’ve been dedicating most of my time to that. For about 3 or 4 months we’ve been writing proposals and trailers and all that. I also have another book idea which I’m cooking up right now, but I haven’t found too much time to do that. I just want to stay in the ocean a little bit longer. I’m not quite ready to hop into something else. I think the potential of these freediving researchers to really make historical scientific breakthrough here is going to be very possible in the next couple of years and I’d love to assist them and be a part of that.

Brett McKay: Awesome. James Nestor, thank you so much for your time. It’s been a pleasure.

James Nestor: Thanks a lot.

Brett McKay: Our guest today was James Nestor. He’s the author of the book Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves. It’s available on

That wraps up another edition of the Art of Manliness Podcast. For more manly tips and advice, make sure to check out the Art of Manliness website at If you enjoy the podcast, I’d really appreciate it if you go to iTunes or Stitcher to give us a review that help get the word out about the podcast. One of the best compliments you could give us is if you would recommend the podcast to a friend or family member. Really appreciate it. Thanks for all your support. Until next time, this is Brett McKay telling you to stay manly.

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