Masters of Technology Happy Hour
Conversations with masters of technology, those who produce it or those who use it.
Masters of Technology Happy Hour
Tetsuo Hara: One Breath To 100 Meters Depth
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And now for something completely different. We hold our breath and go underwater with Tetsuo Hara, champion free diver. Tetsuo is a tech executive by day and in his free time, an elite freediver. He set a Guinness World Record by reaching 100 meters in constant weight at age 58. He explains why deep dives are won with preparation, calm, and systems thinking, not bravado.
• Constant weight freediving basics and what 113 meters feels like under pressure
• How an engineering mindset turns the body into a trainable system
• The real drivers of performance like CO2 tolerance, equalization, relaxation, and lung flexibility
• Training progression that builds confidence by going shallow first
• Why the urge to breathe is mostly CO2 and how training delays the reflex
• Close calls, abort decisions, and the safety logic that keeps divers alive
• Ideal deep dive conditions including warmth, visibility, low current, and free fall
• Pre-competition food and hydration choices plus why scuba holds no appeal
• Lessons from the sport on consistency, community and facing yourself
Welcome And The 100m Record
SPEAKER_01Hello everyone and welcome to the Masters of Technology Happy Hour, where once a week I have a drink with someone I meet in the course of business, but someone I'd like to get to know better as a person.
SPEAKER_00Very nice to see you again.
SPEAKER_01Nice to see you again, and welcome to the show. Yeah, thank you for inviting me. I've had the pleasure of meeting Tetsu at a wedding. He was the brother of a friend of our family, and I met him and his lovely wife and daughter. The most interesting thing about Tetsuo I found is a nice guy, but I also found he has a most fascinating sport, uh hobby, passion, it seems, and it's technically called pre-diving.
SPEAKER_00We hold the breath, and with one single breath, you know, we dive very deep and compete the depth.
SPEAKER_01It's constant weight, correct?
SPEAKER_00Yeah, there's many disciplines, but I do a constant weight, which I use a weight, but I cannot drop it at the bottom. So I have to bring back to the surface again.
SPEAKER_01It's a sport, and you're you're very good at it. You hold the record for the oldest person to dive at a hundred-meter constant wave. Is that correct? That's a Guinness record.
SPEAKER_00Yeah, I made it last year, 58 years and 235 days old. I made that record.
SPEAKER_01Congratulations.
SPEAKER_00Thank you.
SPEAKER_01I think you also uh now I have to see this movie. I think there's a Netflix movie made about diversity.
SPEAKER_00Only a just bit, just a second. At the middle of the movie. Okay, only a second, just a second. I was there. I was competing with the athletes in the movies.
SPEAKER_01That was 100 meters, and you were just 200 meters. Now your record is greater than that, right? 113.
SPEAKER_00Yeah, 113 meters.
SPEAKER_01One one three.
SPEAKER_00Yeah, 113. Right. I think that is uh about 371 feet.
SPEAKER_01Uh what's the pressure down there?
SPEAKER_00About 12 times water pressure than the surface.
Engineering Roots And Business Building
SPEAKER_01So you work for an engineering company. What made you go into this field? Okay.
SPEAKER_00I studied electrical engineering at university, and my father was an entrepreneur and ran an optical manufacturing company. So from a very young age, I watched him build and run a business. Because of that, I always wanted to be become like him to create a company and run business. So I was interested in technology, but not because I wanted to become a pure engineer. I wanted to understand technology well enough to build business around it. Yeah.
SPEAKER_01Did you ever imagine you'd end up as an executive leading engineers, or were you always interested in just the technical side?
SPEAKER_00So after graduating from university, I joined a Japanese general trading firm. In Japan, general trading firm is not just a trading company. It also invests in business and develops new opportunities around the world. So I thought it was the best place to learn the fundamentals of business. About 10 years later, around the year 2000, I started my own venture company in Japan. At that time, NT Dokomo, a Japanese mobile carrier, have launched iMode, which became the world's first commercially successful mobile internet service. My company developed things like mobile advertising, mobile coupon, and mobile membership systems. This was about seven years before smartphone appeared. I wasn't the person writing code. My role was to bring together engineers, sales, marketing, funding, and strategy and turn those pieces into a real business.
SPEAKER_01I talk to engineers all the time. First time I've talked to somebody who's actually diving and doing this for a living. Okay.
Why The Ocean Led To Freediving
SPEAKER_01So most people don't decide to dive deep in a single breath. How did you choose free diving as your hobby or your passion?
SPEAKER_00My connection to the ocean started with windsurfing during university. When there was no wind, I started snorkeling, catching abalone and octopus. But in Japan, steer fishing gradually became more restricted. So I started trying free diving as a sport instead. So at first it was just curiosity, but little by little I got more deeply involved in free diving.
SPEAKER_01It's far removed from what you studied, of course. But did you feel that your education or training gave you any advantage in diving?
Turning Physiology Into An Engineering System
SPEAKER_00Yeah, yes, absolutely. My engineering mindset helps a lot. In deep free diving, performance is not determined by a single factor. It's about several factors multiple together. Like breath holdability, your equalization technique, relaxation, and the flexibility of the lungs. Lung flexibility is especially important at great depth. At 100 meters, the pressure is about 11 times higher than surface. So the air volume in the lungs is compressed to roughly one-eleventh of its surface volume. So if your lungs are not flexible enough, you can injure. And in severe cases, it can become life-threatening. And each of those factors can be broken down even further. For example, blesshold ability includes CO2 tolerance, oxygen efficiency, swimming efficiency, and ability to stay calm under stress. So I really do see the body as a system. If one element is weak, it limits the whole result. That is why freediving is such a logical sport. You have to identify the bottleneck, understand the failure mode, and improve the part of the system that is constraining performance the most. So that way of thinking feels very close to engineering. Analyze the system, identify the limiting factor, test solutions, and keep refining. So it helps a lot.
SPEAKER_01Engineers are real good at math. They have to be. Do you find that you are doing calculations in your head when you're diving? Or do you have instruments that help you make those calculations that you need?
SPEAKER_00You mean during the dive? Yeah. The brain consumes a lot of oxygen. So thinking something during the dive is not helpful at all. So I try to just relax and be empty. Oh just just like meditation.
SPEAKER_01I see. But oh, it's meditating. So it's not like I always think when people are scuba diving that they have to do a lot of calculations about the oxygen mix and the depth and pressure. But you're meditating.
SPEAKER_00Yes, but before diving, we calculate a lot.
SPEAKER_01I've heard that a lot. The brain actually consumes a lot of oxygen when you're thinking.
SPEAKER_00Is that actually the brain consumes more than your muscle?
SPEAKER_01Tell me about your first serious dive, and when you realized this wasn't just a hobby, this you could actually compete at a very elite level.
SPEAKER_00I would say my first serious dive was in 2012, when I competed at Vertical Blue in Bahamas. Vertical Blue is one of the most prestigious free diving competitions in the world, like Wimbledon of Tennis. And at that time, my personal best in constant weight was 70 meters, which is about 230 feet. And that disciplines you dive down and back up on a single breast using a monofin. Even now, free diving is still one of my hobbies I'm most passionate about. I also enjoy horseback riding and sailing. For example, this year I plan to go to Mongolia and do a three-day, 200-kilometer horseback riding across the grass field. So for me, freediving becomes very serious, but it's still one of my great adventures.
SPEAKER_01We'll have to have another show where you tell us about your adventures on horseback, right? All these adventures that involve regular breathing.
SPEAKER_00Yeah, it's gonna be a big adventure in Mongolia.
SPEAKER_01It's a very intimidating sport, free diving.
Training Fear With Small Steps
SPEAKER_01How did you train your body and your mind?
SPEAKER_00Free diving may look intimidating from the outside, but the training is actually very agile. You need to start shallow, maybe five meters, and once you get used to it, then you increase to 10 meters, then 15 and 20. So you don't suddenly jump into deep water. So your body adapts and your mind adapts with the depth. So in free diving, fear is not something you overcome with courage, you reduce it through preparation. For the body, training is about building the specific abilities you need, like breast holding and ear equalization technique and relaxation and swimming efficiency. For the mind, confidence comes from training quality and training volume. So if you have trained enough and if you trust your preparation, you can stay calm during the dive.
SPEAKER_01The vertical blue that you mentioned before, is that when you realized you could compete at an elite level? Is that when you decided you could maybe even try?
SPEAKER_00Yeah, yeah, but 130 meters I made at the Cebu in the Philippines last year. Okay, the Philippines. My deepest record at the vertical blue was 97 meters.
SPEAKER_01Oh, almost there. Almost.
SPEAKER_00Yeah, for most of the deep divers. Yeah, three-digit, which is 100 meters, is everybody's goal or dream.
SPEAKER_01Tell me how the body begins to beg to breathe, convulsions, for example, and how you overcame that urge. Okay.
SPEAKER_00So when you hold your breath, carbon oxide, CO2 gradually increases in your body. That rising CO2 is what triggers the urge to breathe. Interestingly, that urge is not caused primarily by lack of oxygen, it's mainly caused by rising CO2. Through training, your brain gradually learns that higher CO2 levels are not immediately dangerous. As a result, your body becomes more tolerant and the breathing reflects comes later, which allows you to hold your breath longer.
SPEAKER_01Is your body being hurt then by the CO2 consumption? Are you doing any long-term damage? I guess not. You look like you're in pretty good shape.
SPEAKER_00There is no damage. No damage. But if you keep, you know, stop your breathing, you may uh black out. Okay. Yeah, that's the kind of dangerous.
SPEAKER_01I'm an amateur photographer and a woodworker. I have I find many engineers also indulge in photography and woodworking. Our first guest had an outlet in music. Have you met other free divers who are also engineers?
SPEAKER_00Yes. I think there are quite a few engineers in the free diving community. Free diving is a very analytical sport. It requires you to understand diving physiology, the effect of water pressure, and how to train its limiting factor systematically. That kind of thinking naturally appeals to people who enjoy analyzing systems, identifying bottlenecks, and defining performance. So, yes, I have met many free divers who think in a very engineering way, even if the profession is not always engineering.
SPEAKER_01You're the first diver I've met. That the uh you know about Venn diagrams? They say the intersection of Venn diagrams? Mm-hmm. I thought it was zero intersection there between free diagrams, but you've done several.
CO2 Urge Close Calls And Real Risk
SPEAKER_01Is there a high mortality rate in this sport? Is your wife really worried about you? How much insurance do you carry?
SPEAKER_00Unfortunately, most of the insurance doesn't cover the competition. That's really unfortunate.
SPEAKER_01Have you had any close calls?
SPEAKER_00Yes, I have. Several. I talked about one moment. During a dive, my lanyard, which is connecting me to the diving rope, got tangled around the bottom plate at 50 meter depth. So I need to detach it. And when I did, I suddenly realized that I was sinking deeper away from the rope. Since I had no fins in that discipline, I quickly swung back to the rope and pulled myself back to the surface. That was definitely a scary moment.
SPEAKER_01I I am a distance runner, marathons mostly. Ideal conditions for a marathon are uh 50 degrees Fahrenheit, low humidity. What are the ideal conditions for a dive?
SPEAKER_00For a deep dive. The conditions that usually make good performance easier are moderately warm water, no current, and high visibility. Warm water helps the body stay relaxed, and no current means you don't need to waste energy fighting against the current. And good visibility makes the dive feel psychologically easier and more comfortable. There is also a phase in deep free diving called free fall. Usually, once you go deeper than around 20 meters, your lungs compress enough that your body becomes negatively buoyant. At that point, even if you stop kicking, you keep sinking. So instead of swimming, you let yourself fall without moving much. That helps conserve oxygen, which is very important in deep dive. It's also one reason current is not ideal, because during free fall, or any current can disturb your position and make that phase less efficient. For me, that is actually the most pleasant part of the dive. So during free fall, I try to stay completely relaxed and focus only on your equalization. So at a place like Dean's blue hole in the Bahamas, where vertical blue is held, the visibility can be very high. But because it is a vertical hole, after around 40 meters, the light no longer reaches you as well and it becomes very dark. So free-falling down through that darkness feels almost like being in outer space. And when you begin to see the light on the bottom plate, it can look like a spaceship waiting for you in the dark. So in general, moderate water temperature, no current, and high visibility make it easier to produce good results. As for darkness, I think that comes down to personal preference.
SPEAKER_01Tell me about the darkness. So light doesn't penetrate past a certain depth. Did you say 40 meters?
SPEAKER_00Uh in case of blue hole? Yeah, yes, 40 meters.
SPEAKER_01Okay. And you have no light source on your body?
SPEAKER_00Yes, I do. I have a torch light on the head attached to my wetsuit.
SPEAKER_01Oh, I see. So you can always see the rope and and this I have depth markings on the rope.
SPEAKER_00Yeah, so I can only see the rope in front of me. That's it.
SPEAKER_01Have you ever aborted a dive midway?
When To Abort A Dive
SPEAKER_00Yes, I have. Equalization problems are the most obvious sign. If my ears don't equalize properly, I make early turn immediately. Because if I force it any further, the risk of rupturing my eardrums becomes much higher. But that is not the only reason. If the sensation around my lungs feels different from usual, or if I can't not fully focus, those are also signs that I should turn early. In free diving, pushing a dive when something feels wrong is usually a bad sign. So if something feels off, I would rather turn early and save it for another day. It's not about proving anything on one dive. It's about being able to keep diving safely for the long term. Yes.
SPEAKER_01You're a wise man. I think a lot of people that practice sport don't uh don't have that uh outlook. They'll they'll take a lot of risks. Tell me this about you said uh equalizing, equalizing that's the pressure of the inner ear to the water pressure. How often does that happen where your ears don't equalize?
SPEAKER_00In the beginnings, you have to equalize often because water pressure changes a lot, but when you go deeper and deeper, the pressure changes gradually, little by little. So the so that means uh you don't need equalize often in the great depth.
SPEAKER_01I see. Is a pressure in your ear equalized by through the uh station tube in the mouth?
SPEAKER_00Yes, yes.
SPEAKER_01Okay, and sometimes that doesn't happen.
SPEAKER_00So you have to push your your air from the mouth to ear. Okay. But when you go deep and deep, your air in the mouth gets smaller and smaller. So your air is not enough to push your eardrums. That happens in the last moment. I see.
SPEAKER_01You have to learn a little bit about medicine and physiology then with the sport. Like I said, I I ride my bike for long distances. So far, I've resisted getting an electric bike. To me, does that to electric bike seems like scuba diving, diving with scuba tanks. Would you ever go diving with a scuba tank now?
SPEAKER_00Yes, I have a certificate, but I've never tried after I got licensed. Actually, only do I do it freediving, no scuba. So to me, scuba diving is a completely different activity. What I love about freediving is its simplicity and the way it lets me face myself. One breath, one body, one descent. So scuba is most about more about exploration, which I can understand and expect, but it's not what attracts me personally. So at least for now, I don't feel much temptation to add tanks. What interests me is the purity of doing it on a single breeze.
SPEAKER_01How do they test you to make sure you haven't been too reckless? You have to, there's a protocol when you come out of your diet, correct?
SPEAKER_00Yeah, in competition, you can only announce a depth that is about three to five meters deeper than your. Seasonal best. So you cannot make a reckless jump. And the diving rope is set only to that announced depth. So even if you feel great, you cannot go beyond it. Even if the ocean condition looks the same, it doesn't mean your body is the same as yesterday. Just because you could reach a certain depth yesterday doesn't mean you should assume you can do it again today. Your physical condition changes every day because of fatigue, recovery, mental focus, and stress. In that sense, your condition rises and falls almost like the tide. So the sport has external rules to prevent recklessness, but it also demands honest self-awareness. You have to understand where you are physically and mentally on that particular day.
SPEAKER_01You're also affected by what you eat,
Food Hydration And One Breath Simplicity
SPEAKER_01correct? Do you certain foods produce gas, which could be a problem?
SPEAKER_00Yeah, that's affect a lot.
SPEAKER_01Do you uh do you have take any precautions and uh do you have a regular diet that you follow before a competitive uh diet?
SPEAKER_00Yeah, especially before the day before the competition, I really avoid like a meat because it takes time to how to say, how to say digest? Yeah, digest it.
SPEAKER_01Is the goal to not have any food in your systems?
SPEAKER_00Yeah, before that I try not to eat much. Only one banana, that's it. But at least three hours before the competition, I don't eat anything. I don't eat anything.
SPEAKER_01How about hydration? Is that a factor?
SPEAKER_00I get enough hydration.
SPEAKER_01What effect does the diving have on your the hydration of your body? Does it you're in water, but you're also at a ridiculous temperature.
SPEAKER_00Because we wear wetsuits, we sweat, we get sweat a lot. So having uh hydration is very important. Oh, you sweat in there? But these are warm waters you're diving. Because because most of the place we compete is the how do you say, hot place like Bahamas or Cebu, yeah, like uh like 30 degrees Celsius? So it's hot. But under the water, like 100 meters, the water temp is getting cold.
SPEAKER_01So we wear the I imagined ocean depths is quiet. Is that actually the case? Or is that what and what is going through through your mind? You said meditation, right? But are you meditating in a in a calm environment or is it noisy down there?
SPEAKER_00Deep water is very quiet. At those depths, you usually don't see many fish, and the world feels extremely still and isolated. It can feel lonely, but in a beautiful way. As for what goes through my mind, ideally almost nothing. As I said, the brain uses a lot of oxygen, so thinking too much is not helpful for free diving. So I try to stay relaxed and empty, like I said, meditations. So, in that sense, a deep dive is not a place for many thoughts, it's more a place for presence.
SPEAKER_01Has diving taught you anything that engineering could not?
SPEAKER_00Yeah, the biggest lesson is simple. It's consistency is power. At 50 years and 235 days old, I got uh Guinness World Record, and uh I became the deepest person in history to dive deeper than 100 meters. But that achievement was not talent, it was accumulation of experience. The ocean changed every day, currents, temperatures, visibility. The more conditions you experience, the more your body learns. And another important lesson is the importance of community. Free diving is an individual sport, but you cannot train alone. Safety divers, training partners, and teammates are essential. So having people with the same passion and pushing each other forward is incredibly valuable.
SPEAKER_01That's what I learned. That's all the questions we had prepared. Anything else you'd like to add about what your sport and your I have two daughters.
SPEAKER_00Do they free dive or do you they they have no interest in freediving, unfortunately?
SPEAKER_01Unfortunately.
SPEAKER_00But I tell you that young people uh like to compete with other people, but I as I said, this sport is more to face yourself. So when you get older, you can enjoy more about free diving. I think my daughter is too young to enjoy this sports.
SPEAKER_01I I know how you feel because uh when I try to get my children interested in long-distance cycling or long distance running, it's just too boring for them. I they can't, they're not interested in you know, running on pavement for hours at a time, or you know, riding a bike with uh on a road for all day long. It's it's that's not what they want to do at all.
SPEAKER_00So the bicycles maybe you have to face yourself. Yes.
SPEAKER_01I think when you get older, you get used to it's not boring anymore, it's more tranquil and peaceful. And and I appreciate that what you said about diving, that you actually can meditate, because I found that to be my yoga, what I wanted to replicate. It was like it was very uh peaceful for me, and I could think clearly.
SPEAKER_00It's really interesting to face yourself, like your ego and your impatience, yeah. Everything you have to face.
SPEAKER_01Yeah, I enjoy I enjoy the discipline too, like you do. The discipline of your to make your body do things to see what the limits of your body are. It's very uh gratifying. Yeah.
SPEAKER_00And I really enjoy the process, you know. I improve my limiting factors. It takes time, like every year I improve a little bit. You're still improving? Yeah, I still improving. Uh-huh. Okay. Yeah. As I said, my record was made last year, last summer.
SPEAKER_01Yeah.
SPEAKER_00Three meters deeper than previous year. So three meters improvement. But that before, my personal record was 97 and I jumped to 110. I started to having my coach teaching me uh how to swim better with my monofin. Yeah, that affected a lot.
SPEAKER_01I see. Performance. That's for marathoners, that's like uh that's a big change. 10 10 meters. Uh for marathoners, yeah, most 15-minute changes in marathon time.
SPEAKER_00Yeah, most of athlete the performance is very affected by those coaches, right? Even the Olympia.
SPEAKER_01Yeah. Yeah, even Olympians.
Costs Competition Life And The 116m Goal
SPEAKER_01Okay, is this a rich man's hobby? You have it when you dive. Is it an expedition? Do you have to pay a lot of money to do this?
SPEAKER_00It really depends. Yeah. Actually, you don't need to have much equipment like scuba. You only need your fins, wetsuit, and goggles. That's it.
SPEAKER_01That's it.
SPEAKER_00Yeah, you can pay for your coach, but it depends on the coach. But even without a coach, you can enjoy in the ocean, and ocean is free. But if you uh rent a boat, you have to pay. But you can have an entry from the beach. It's not for our rich people, it's for everyone.
SPEAKER_01I'm watching this movie, The Deepest Breath, right? And uh and I see people like when they come up to the surface and they get ask them the questions, are you okay? Uh, or I think they ask them specific questions.
SPEAKER_00No, no, no. So after A3 get on the surface, yeah, they have to take out the all the equipment, like the goggles and note script out of your face and make an okay sign on the with the fingers, and you have to say, I'm okay.
SPEAKER_01You have to say I'm okay. Okay. That's it. They don't make but they don't make questions, like math questions or so.
SPEAKER_00No, there's no question, but you have to do the same protocols. I see. But when you are out of oxygen, uh-huh, it's really hard to make that protocol.
SPEAKER_01How many divers are there in like the like some of these competitions?
SPEAKER_00It depends on the competition, but usually 40 people or 50.
SPEAKER_01How much is the entrance fee?
SPEAKER_00It depends on the size and the place of the competition. The case of uh like a Baltic Blue, about 1,000 US dollars. But other ones like in Cebu, about $500. Because the competition is in Bahama costs a lot because you have to gather all the people from around the world. Bahama is very far from any countries.
SPEAKER_01Yeah, you have to go halfway around the world for that. So basically, you just have the cost of getting yourself, getting to that location, staying on board, acclimating to the water perhaps for a couple of days, and then just do the diet.
SPEAKER_00In my case, because I have a business, yeah, you know, freedom is not a business. I am just uh it's just a hobby for me. And I have a daily business, so I cannot take uh rest for long. So usually uh for like uh for the Bahama case, so before the competition, maybe three days before the competition, I uh I go to Bahama and train three days and then competition. But most of uh athlete, it's not just a hobby, most of them is uh professional athlete as a freelancer. So those people come like one month prior to the competition and they train for a period of one month. That is uh very high advantage for them.
SPEAKER_01Obviously, if you have a job, you can you can't do that. What's next for you? Are you going for uh 116 or 103?
SPEAKER_00Yeah, 116, 116 is my next goal, okay, which is uh Japanese record for men. So 113 113 meters is the deepest among active free divers in Japan, but one man who already already retires made 115. So I try to make 116, one meter deeper than his record.
SPEAKER_01Now that's for any diver, any male diver, not age group.
SPEAKER_00No, he's young, much younger than me, but he already retired.
SPEAKER_01Good luck with that. When are you gonna plan? When is this happening?
SPEAKER_00In August in Cebu. Oh, where is Sabu? Philippines. Very famous place for scuba diving.
SPEAKER_01All right, Tatsu. Well, this has been great. Thank you so much for joining me.
SPEAKER_00Yeah, thank you very much for inviting me. I really enjoyed it.
SPEAKER_01And that concludes this episode of the Masters of Technology Happy Hour. I hope you enjoyed our chat and will join me as we talk to some of the most interesting people in the design and engineering software community.