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This month we take a plunge into the wild world of freediving. You are holding your breath, aren’t you? In our view, the diving community writ large can arguably learn a lot from freedivers…



Text by Michael Menduno. Header image by Lorenzo Mittiga, who provided photos used through out the FREE story bundle.

Diving into the wild! photo by Lorenzo Mittiga

This month we take a plunge into the wild world of freediving. You are holding your breath, aren’t you? In our view, the diving community writ large can arguably learn a lot from freedivers who have essentially operationalized their knowledge and their ability to manipulate mammalian physiology to significant effect. Today’s top athletes are all pushing beyond 100 meters, even intermediate freedivers are reaching into tech diving depths of 50 m/164 ft and beyond, and five-and-six minute static breath-holds are not uncommon—the men’s record is 11:35 (11 minutes, 35 seconds) and women’s record 9:02, breathing up on air. Nitrox pre-breathing is still in its infancy.

As a result, like the old recommendation for early tech divers: Take a cave diving course whether or not you intend to cave dive!—every tech diver should strongly consider taking a freediving course! Without a doubt, it will increase your depth of knowledge and give you a visceral experience you won’t soon forget—a two and a half to three-minute static apnea breath-hold (three minutes qualifies you for intermediate level) will give you an entirely new appreciation for the power of CO2 and your urge to breathe. I guarantee it!

You may find it surprising that freedivers are every bit as geeky as their tech diving counterparts. A few years ago, I had the opportunity to cover and report on Performance Freediving International’s (PFI) Deja Blue Competition in the Cayman Islands for an Alert Diver freediving story. There I was housed in a condo with the rebreather safety diving team. They were a small team of Canadian tech divers led by Bill Coltart who were tasked with being deep safeties for the event. During the competition, the safeties took turns being stationed at 50-80 m/165-261 ft, depending on the event, armed with a lanyard and lift bag to rescue a freediver in the event of an incident at depth. 

One night, we were sitting around the kitchen table strewn with rebreather equipment, and I took notes as the divers engaged in animated discussions about hyperbaric sensor calibration, the efficacy of hypoxic training, comparative work of breathing, whether cartridges offered advantages over hand-packed scrubbers, and the accuracy of temp sticks. After a time, I was curious to know how the freedivers were faring, so I walked next door to the athlete’s condo.

So many fish, so little time.. Photo by Lorenzo Mittiga

To my delight, a half dozen competitors were sitting around the kitchen, watching videos from the day’s dives and geeking out on their equipment as well, in this case their bodies. Their discussion ranged from sharing Frenzel equalization secrets, the optimal depth for moving a mouthful of gas from their lungs to their mouth on that 80 m/262 ft dive in order to equalize, their preferred Mucinex regiment, the agony and ecstasy of doing negative statics, their last samba i.e., LMC (loss of motor control), and their plan to break their PB (personal best) on tomorrow’s dive. It was clear—they were every bit as geeky as their tekkie counterparts.

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In this issue of InDepth, we offer you a curated selection of freediving stories that we thought might be of interest to tech divers, beginning with a Wim Hof-inspired story by Sabrina Figliomeni titled, “Freezedivers: What Doesn’t Freeze You Makes you Stronger.” Beware: it will potentially make your blood run cold, even if you’re wearing your RF1!

Next science writer Reilly Fogarty tackles the issue, “Do Freedivers Get Bent?” and explores what we know and we don’t know about breath-hold DCS. The answer is yes btw! French adventure writer Florine Quirion introduces the next innovation in freediving biometrics in, “Listen Up: Freediving Is About to Enter a New Era if Oxama has a Say!” Then we dive into Ted Harty’s Freediving Summit, with a pair of reports, “How Do Competitive Freedivers Stay Safe?” by tekkie turned freediver Dean Laffan, and Handling The Pressures of Competitive Freediving by freediving freelancer Charly Stringer. 

We conclude with some resources on Technical Freediving i.e, breath-hold dives conducted with nitrox pre-breathing, and a The Diver Medic’s new DAN Europe-approved Freediving Emergency Medical Responder course.

Finally, a special thanks to Bonaire-based photographer extraordinaire Lorenzo Mittiga for supplying us with a bevy of freediving bella foto. Grazie Lorenzo! That said, I suggest that you do a good breathe up and dive right in.—M2 

Do Freedivers Get Bent?

by Reilly Fogarty

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Technical Freediving

Kirk Krack and John Hullverson about to conduct mixed gas freediving operations on the Nippo Maru, Truk Lagoon.

The freediving community is the latest community to begin applying mixed gas technology to improve their safety and performance. It’s fair to say that at this stage mixed gas freediving, specifically nitrox freediving, is still in its infancy, and only used by innovators like freediving pioneer Kirk Krack, who has used nitrox pre-breathes successfully in film work on James Cameron’s Avatar series, his colleague John Hulverson and others. However, this will likely change as freedivers learn about and are able to experience the benefits of nitrox pre-breathes. Watch this space.

Tech freediving articles:

DeeperBlue: Technical Freediving: Are Breathhold Divers Ready To Mix It Up? By Michael Menduno (2019)

DeeperBlue: Technical Freediving In Hollywood Revealed by Victoria Brown (2020)

Diver: Technical Freediving in Truk Lagoon By Kirk Krack and John Hullverson (2019)

JHPEE: Covington D, Lee, RH, Toffell S, Bursian A, Krack K, and Giordano C Technical Freediving: An Emerging Breath-Hold Diving Technique, Journal of Human Performance in Extreme Environments: Vol. 15: Iss. 1, Article 3 2019 DOI: 10.7771/2327-2937.1122

Alert Diver: The New Pointy End of Diving by Michael Menduno (2017)

Tech freediving videos and webinars:

The Diver Medic: Kirk Krack – Technical Freediving

Dirty Dozen: Episode #9: Kirk Krack; Technical Freediving in Hollywood with Aron Arngrimsson

OZTek: Video interview with Kirk at Oztek by Michael Menduno 

Freediving Emergency Medical Responder course (FEMR)

This agency-neutral course which was developed by The Diver Medic is endorsed by DAN Europe, many dive doctors and safety specialists, along with Italian freediving champion Andrea Zuccari.

Breath-hold diving is a rapidly growing sport around the world whether freediving for fun or competition freediving. There is also spearfishing, synchronised swimming, and of course, mermaids that freedive professionally for aquariums and events. There are hundreds of thousands of breath-hold divers in the world; many push themselves to their limit, either hunting for food or setting personal records for depth or time. 

However, breath-hold diving has a huge risk factor—possible death or serious injury! This form of diving suffers from an alarming number of fatalities. According to the 2019 DAN Annual Diving Report, there were at least 955 breath-hold diving incidents between 2004-2017, with 73% fatal outcomes—or an average of at least 51 fatalities per year. [Ed.note: This is not the case in freediving competitions] Of course, those are the recorded incidents, what about the unreported ones?

What are the other risks? Blackouts and hypoxic fits, dehydration, blood sugar levels, barotrauma to the eyes, ears, sinus, and lungs, nitrogen narcosis, decompression sickness. Hood squeeze and mask squeeze. Cuts, abrasions to catastrophic injuries like marine life injuries or being accidentally shot with a speargun. Cardiac arrest, heart attack, anaphylaxis, hypothermia, hyperthermia, and shock to name a few. 

Yes, most sports have risks but would you know what to do in an emergency? This is why we want you to be prepared and continue to enjoy the sport you love so much. We encourage you to be safer with the knowledge that can change the outcome of life or death. 

Here are the links to the  courses:

Freediving Emergency Medical Responder

Spearfishing Emergency Medical Responder


Why Tech Divers Should Take A Freediving Course

The tech community can arguably learn a lot from freedivers who have operationalized their knowledge and their ability to manipulate mammalian physiology, to significant effect. Today’s top athletes are all pushing beyond 100 meters feet, while even intermediate freedivers are reaching tech diving depths. That’s why we recommend that every tech diver should take a freediving course. Freediving educator Ted Harty explains why.




By Ted Harty. Lead image courtesy of Lorenzo Mittiga. Other images courtesy of Ted Harty.

Hey there, tech diver! 

You and I both started as scuba divers.

Then, we both decided plain old “regular” scuba diving wasn’t enough for us.

You decided you wanted to go deeper and stay longer.

You decided if one tank was good, eight tanks were better.

You decided you wanted more math in your dive planning.

You decided you wanted way more gear.

You decided you wanted a new type of diving where a mistake might kill you.

You decided you want to spend way more money to go diving.

You decided going into tiny, tight places sounds like fun!

You are kind of crazy.

Remember that the next time you say those freedivers are “crazy”.

I took a different path. I taught scuba in the Keys for several years. Paychecks in paradise, beers and bikinis, I bought it hook, line, and sinker; I was an easy mark. Eventually, I started freediving and that changed my life more than any choice I have ever made.

Today, my job is to convince you that you should try freediving for two reasons:

#1 It’s awesome.

#2 It will make you a better tech diver.

My name is Ted Harty, and I’m the founder of Immersion Freediving and my pride and joy, which is a free online coursed that will teach you how not to kill yourself while freediving and how to save your buddy’s life if they blackout. Don’t worry, more on this fun topic later. I’ve appeared on the Discovery Channel training Tim Kennedy, worked with Jack Dorsey, ex-CEO of Twitter, and trained Ben Greenfield.

Before we get into why you should try freediving, let me handle the most common objection I get: “Ted, freediving looks awesome, but I’m too old, I’m too out of shape, I can only hold my breath for 45 seconds.” If you want to be a world record freediver then yes, you need to be an elite athlete. If you just want to be a regular old freediver, you don’t.

I have a body built by beer, bourbon, and BBQ, yet my deepest freedive is 85m/279 ft, and my longest breath hold is 7 minutes. My average student after my 4-day PFI intermediate class does a 4-5 minute breath hold and a 30m/100 ft freedive. At the recreational level, being a good freediver is mostly about knowledge and technique, not rare athletic ability. 

Let’s get started!

SACR and DACR rates, anyone?

Tech divers obsess about how much oxygen they are using. Guess who obsesses about that more than you do… FREEDIVERS! 

We use many techniques to reduce our oxygen consumption. Freedivers spend a lot of time focusing on our breathing, especially before a dive.  I always say the biggest secret to holding your breath is not what you do during the breath hold, but what you do before the breath hold.

“The biggest secret to holding your breath is not what you do during the breath hold but what you do before the breath hold.”

We learn how to use our breathing to slow down our heart rates, which reduce our oxygen consumption.

We also know how to increase the oxygen carrying capacity of our blood, more on that below.

After I took my freediving class and applied the breathing techniques I learned, I immediately lowered my air consumption while scuba diving.

You have to understand I was a dive instructor at the time and was diving almost every day year-round, and I even noticed an immediate improvement. 

If you want to lower your surface air consumption rate (SACR) and depth air consumption rate (DACR) learn freediving breathing techniques.

Physiology Over Physics

I admit tech diving has more math and physics than freediving does, but freediving has way more physiology than tech diving.

Kirk Krack, founder of PFI and a tech pioneer, says that there is more physiology taught in a PFI Intermediate class than in the upper levels of tech diving.  The coolest topic we dive into is the mammalian dive reflex.

Dolphins, seals, and whales are mammals. We are mammals. Dolphins, whales, and seals have the mammalian dive reflex. It’s used to turn these mammals into freediving machines. Genetically encoded in every single human being is the mammalian dive reflex. You need to know how to turn that sucker on, so you turn into the freediver you were born to be.

When the dive reflex is active, the blood vessels in our fingers and toes constrict, pushing blood to our core to keep the heart, lungs, and brain supplied with oxygen. The dive reflex causes bradycardia, a fancy name for slowing of the heart. It does this to minimize our oxygen consumption. Sound useful for tech diving?

Our spleen contracts, which pushes more red blood cells into your blood. This raises the oxygen-carrying capacity of our blood. We get free and legal blood doping just by freediving. How cool is that! You’ll learn about these adaptations and how to apply them to your diving in a freediving class. 

How To Activate Your Most Primal Reflex Before You Dive

Try doing three to four breath holds before you get in the water before your dive; that will start to kick in the dive reflex.

Breathe for two minutes, then hold until you have an urge to breathe. 

Breathe for three minutes, then hold until you have an urge to breathe. 

Breathe for four minutes, then hold until you have an urge to breathe. 

Breathe for five minutes, then hold until you have an urge to breathe. 

That would for sure kick in your dive reflex, but does take some time.

Another way is to breathe with your face immersed for five minutes with your mask on your forehead and your snorkel in your mouth. That water across the eye kicks in the dive reflex as well. Not as good as doing the breath hold, but at least you can get it going in five minutes before you go.

Kirk talks about having tech divers do this to kick in the dive reflex to lower air consumption and calm the mind before a dive. [Ed.note: Legendary cave explorer Sheck Exley used to do this before big dives.]

No Gear!!!

When I first started getting into freediving I was working as a dive instructor in the Florida Keys. I loved that on my day off, all I needed was a mask, fins, snorkel, and I could hop on my boat and go. No need to go to the dive shop to get my tanks filled.

Don’t get me wrong; I still like to put my tanks on to go hang out on a deep wreck, but if I want to play around 10-21m/30-70 ft, I’m freediving at that depth all day long with minimal gear.

Scuba diving is the integration of human and machine. In freediving, the human becomes the machine.

“Scuba diving is the integration of human and machine. In freediving, the human becomes the machine.”

Freediving And Scuba Diving Do Not Mix

Let’s say you are coming up from a  wreck dive. Do you come up fast or slow? SLOW!

What do you do at 5m/15ft? Safety stop.

Now, do you get on the boat, take off all your gear, and decide you’re going to freedive down to the top of the superstructure at 24m/80ft?

Question: when you take all your gear off, does the nitrogen magically come out of your body and attach itself to the tank and BC? Of course not!

But nevertheless, you freedive down to the wreck and then come up.

Do you come up fast or slow? FAST!

What do you do at 5m/15ft? Fly to the surface.

If you go freediving after scuba diving, you are asking to get bent. All the nitrogen is still in your body. I know of scuba instructors that got bent in the Keys doing exactly what I described.

Let’s address scuba diving after some freediving.

Here’s the issue: no one knows how much nitrogen freedivers are absorbing. There is no computer that tracks it, and DAN doesn’t know. However, we do know that  freedivers get bent.

So, if you go freediving, you are absorbing some unknown amount of nitrogen, so you can’t properly plan for your upcoming scuba dive.That’s why I teach my students to freedive and scuba dive on separate days.

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How To Get Started Freediving

I’ve included the steps on how to help you get started into freediving and some resources that will help you along your way.

Step #1 Safety

All great freedivers are safe freedivers.

Many freedivers are not safe, here is why.

While every scuba diver is REQUIRED to take a class with an instructor, pass a written test and be evaluated by an instructor in the water proving they can handle all emergency situations and rescue someone in need. The big difference is 90% of the people that freedive have not taken a freediving class. 

They just walk into the dive shop and say I want those big fins, the tiny mask, the camo wetsuit and the biggest speargun you got. The dive shop swipes their credit card and it’s now on them to figure out how to not kill themselves while freediving.

See the difference?

Scuba divers can run out of air which can lead to a fatality unless they have procedures set up in place to prevent this issue.  When Freedivers can run out of air, they experience shallow water blackout

If a freediver doesn’t have a buddy there to watch and be available in the case of a blackout, it can lead to a fatality as well. On the other hand, if the freediver has a buddy right there, disaster can be easily averted. it’s incredibly easy to fix.

After working on a dive boat in the Keys for three years, I can assure you that rescuing someone from a blackout is infinitely easier than rescuing a panicked snorkel or scuba diver at the surface.

To learn the truth about shallow water blackout, for example, how to tell if you are wearing too much weight, and how to save your buddy’s life if they blackout, please check out  It’s not a substitute for taking an in-person course but it’s a great start.

Step #2: Equalizing

Wait, wait, I can see the eyeballs from here. “Ted, I’m a tech diver. I can already equalize fine.”

Question: How deep will you be able to freedive if you use the Valsalva equalization method?

Answer: Likely no deeper than 9m/30ft! I’ve had probably five scuba instructors in my class get stuck at 5m/15ft because they were using the Valsalva method of equalizing, not the Frenzel method of equalization.

The dirty little secret in freediving classes is 20-40% of the students will get stuck at 5-9m/15-30ft, unable to equalize head down.

Freedivers must use the Frenzel equalization method if they want to equalize instantly and effortlessly head down.

So yes, YOU, the mighty tech diver who can dive to 300ft, can easily get stuck at 5m/15ft in your freediving class if you are not doing Frenzel.

Here is a short YouTube video to allow you to figure out which method you are using: Valsalva vs Frenzel Method of Equalization. If you are using Valsalva, there is an online course that will teach you how to switch from Valsalva to Frenzel: Roadmap to Frenzel 

Step #3: Get your freediving questions answered.

Each episode of my podcast, Freedive Live, I answer  the most common questions I’ve been asked over my 15 years as a freediving instructor. 

Step #4: Take a freediving class.

I’m not currently teaching physical classes. I’ve moved to the North Georgia Mountains and there isn’t a lot of good freediving up here. However, here are some freediving classes I recommend. If you try any of them, please let me know how it goes. 

evolve FREEDIVING (PFI North Carolina)

SoCal Spear-It (PFI California)

East Coast Divers (SSI & PFI Boston)

BlueAlchemy Freediving (PFI Virginia)

Florida Freedivers (PFI Palm Beach FL)

Bluewater Freedivers(PADI Florida)


Freediving Instructors International—Daniel Koval (FII Hawaii)

Freediving Instructors International-Errol Putigna (FII Florida)

Step #5: At-Home Freediving Training Programs.

If you want to get the most out of your upcoming course, or if you have taken a course and you want to learn how to get better, I can show you how. My Freediving Training Secrets is a guided, freediving-specific training plan you can do from home. No pool or ocean required. I also create daily freediving advice videos on the following platforms:

Dive safe out there!



InDEPTH: Is Freediving Safe? by Ted Harty


InDEPTH: Doping for Depth by Charly Stringer Technical Freediving: Are Breathhold Divers Ready To Mix It Up? By Michael Menduno

AIDA: WORLD RECORDS: AIDA official World Records History

Ted Harty began his professional underwater career as a Scuba Instructor for PADI, NAUI, and SSI in 2005. In 2008 he took his first freediving class with Performance Freediving International. After that course, he wanted to go freediving instead of scuba diving on his days off, and realized his passion was freediving. In 2009, Ted took PFI’s first official Instructor program, and immediately started working for PFI helping Kirk Krack and Mandy Rae-Kruckshank teach courses all across the USA.

Ted went to his first freediving competition in 2009 as an overweight, out of shape scuba instructor and progressed from 24-27 m/80-90 ft freediver to 54 m/177 ft in three weeks. After the experience he wondered what he could do if he actually started training. Since that time, he’s broken a USA Freediving record in 2011, won three freediving competitions, and was selected to be the captain of the USA Freediving team in 2012; his deepest dive is 85 m/279 ft. Lately, Ted has been focusing on spreading his message of safe freediving through, which offers a free online course sharing all of the safety information he teaches in his in-person classes. He can be reached via Facebook, Instagram, Youtube, and Twitter, @ ImmersionFD. Email:

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