by John Hullverson

The PFI crew just returned from an EPIC trip to freedive the sunken Ghost Fleet of the Truk Lagoon. Truk Lagoon, in modern day Chuuk State, Micronesia, was the site of a decisive WWII battle between the US and The Empire of Japan on Feb. 16-17, 1944.  Code-named Operation Hailstone, the attack was essentially the US version of Pearl Harbor, with US planes sinking an entire armada of Japanese ships in the shallow waters of this atol lagoon and destroying hundreds of Japanese aircraft on the ground and in the air.

Chuuk state in Micronesia

Seventy three years later, Truk lagoon is regarded as the most well preserved battleground wreck diving site in the world. Scores of ships and planes lie mostly intact and undisturbed in less than 200 feet of water, filled with cargo including fighter aircraft, tanks, bulldozers, railroad cars, motorcycles, torpedoes, mines, bombs, boxes of munitions, radios, thousands of various weapons, human remains, and other artifacts.  The ships themselves serve as artificial reefs and the amount of sea life is astounding.

Anti-aircraft guns on deck

For years, our good friend and leader of the safety rebreather team at our annual Deja Blue events, Bill Coltart, of Pacific Pro Dive, has been tempting us with stunning photos and amazing stories of his bi-annual trips to Truk.

Finally, we couldn’t take it any more and had to see these amazing wrecks for ourselves.  Naturally, though, we’re freedivers, so we had to design an expedition that would focus on exploring these sites on a single breath of air.


This wasn’t a minor task, though, because although there are many wrecks in the 10 to 25 meter depth range, there are plenty more between 30 and 60 meters.  While a “touch-and-go” freedive to 60 meters is one thing, having quality time at depth to meaningfully explore these wrecks is quite another, and would require some creativity and planning.  Fortunately, we’ve been developing a couple protocols that would make this possible:  Scooter Freediving and Technical Freediving.


Scooter Freediving

If you’ve joined us for our annual training camp and competition Deja Blue in Grand Cayman the last several years, you know we’ve been utilizing Dive Xtras underwater scooters to provide deep safety to all our athletes on their dives.  That means one of our scooter safety freedivers accompanies the competitor nearly the full length of their dive, down to at least 60 meters, and often deeper than that.  Dive Xtras’ new Piranha scooter is a perfect tool for that job as it weighs less than 35 lbs, and is fast, durable and reliable.  We’ve become pretty adept at using the scooters recreationally to explore the reefs and wrecks around Cayman, so they were the perfect choice to help us effortlessly get down to the deeper wrecks of Truk and explore.

John Hullverson exploring a giant propeller on the Heian Maru

Technical Freediving

We’ve also been developing a new protocol for what we call “Technical Freediving.”  Technical Freediving is breath-hold diving while also using enriched oxygen mixtures as surface breathing gasses to help flush nitrogen and increase the availability of oxygen to the tissues. Used both before and/or after a freedive, enriched O2 mixtures (most commonly Nitrox 32% or 36% pre-dive and 100% 02 post-dive) can reduce fatigue, decompression stress and surface intervals while both increasing breath-hold times and speeding recovery.  PFI has been testing our protocol for several years and our Deja Blue safety freedivers have been utilizing pre-dive Nitrox with great success the past two seasons.

Kirk Krack ascends from a tour of the Hoki Maru
toward his 02 recovery gas

We were really excited to freedive Truk with the expectation that by employing scooters and technical freediving, we would achieve dive times of up to 5 minutes (and maybe longer) — plenty of time to meaningfully explore the wondrous wrecks we were about to see.  We were not disappointed!


The Truk Master

After a pretty manageable flight to Hawaii, and then a restful overnight in Guam, we arrived on Truk at 10:00 a.m.  After a 5-minute drive and an equally short tender ride, we were soon aboard our floating home for the next 10 days—Master Liveaboard’s Truk Master

Master Liveaboard’s Truk Master

This 121 ft dive yacht was perfect for our needs.  Really comfortable cabins, super friendly and attentive Captain and crew, plenty of space for all the various cameras and equipment and an executive chef intent on making our trip a weight-gainer!


Technical Freediving on the Wrecks

Over the course of 10 dive days, we dove on 17 wrecks, from 3,700 ton merchant ships like the Nippo Maru, to Japanese Zeros and Betty Bombers, and even a sunken submarine that still contains the remains of the unfortunate crew who all perished when their commander, fearing an imminent air attack, ordered the sub to dive before all the hatches were closed.


During our dives around and into the holds of these wrecks, we saw tanks, trucks, a bulldozer, land mines, millions of machine gun bullets, crates of beer bottles, a whole range of machinery, supplies and personal effect such as medicine bottles and fine china dinnerware. And yes, even human remains, which served as a sobering reminder that the wrecks we were enjoying were sunk during a ferociously intense battle that must’ve seemed like hell on earth to the men onboard.

Our dive days began with the Captain briefing us on the particular wreck we’d be diving, followed by a “team meeting” between the freedivers and rebreather crew to go over the specific dive and safety plans we’d be following.

Next, it was out onto the huge dive deck to suit up and get our equipment prepared for the dive.  For technical freediving, that included analyzing tanks to ensure the proper mix of gases we’d be breathing before and after our dives.

Our rig consisted of two sturdy Gannet floats supporting a 5-meter carbon-fiber bar that serves as our “home base” in the water.  Attached to the carbon-fiber bar are mounts for the two tanks —one Nitrox for pre-dive breathe-up and one 02 for post dive surface recovery.  We attached the rig to the mooring buoys which usually led to the to deck or King posts of the wrecks.

After a suitable warm up, Kirk, Chris and I took turns exploring the amazing underwater playground.  ONE IMPORTANT NOTE ABOUT SAFETY:  Technical Freediving and freediving in overhead environments, such as the interior of sunken wrecks, requires specialized knowledge, training, expertise and planning and should not be attempted in the absence of any of these factors.

Our typical dive began with an appropriate surface interval followed by a breathe-up and peak inhalation taken directly off the Nitrox regulator.  The scooters allowed us to get down to the wrecks usually within about 20 seconds, and from there we followed a predetermined plan of exploration of the wreck, usually either a tour of the deck, on which sat various equipment like tanks and anti-aircraft guns, or an exploration of the interior holds and passageways of the ships which held an amazing variety of cargo from airplanes and airplane parts, to landmines to torpedoes and periscopes.

The technical freediving and scooters had their intended benefits and we were excited to be enjoying dives of more than three minutes with complete ease.  That’s a significant amount of time observe our surroundings and the scooters allowed us to cover a lot of territory.  It was not uncommon that we could completely circumnavigate these large  vessels on a single dive. Here’s a great video of Kirk doing just that around the 107 meter long Nippo Maru—check out all that gear on deck—tanks, howitzers and more, and realize, as the title describes, this was done on a single breath.

Highlights of the trip

Some of the highlights of our trip include exploring deep inside the various engine rooms (always keeping a clear view of the route to the blue water outside) as well as zooming down the outer gangways to explore the whole length of the ship.  It was fascinating viewing the torpedo holes in the hulls or massive bomb craters in the decks that brought these enormous ships to the bottom.   On our last dive day, Kirk and I were diving the Hoki Maru, a 137 meter long merchant ship resting at 50 meters deep.  By this time in our trip, we had seen almost everything there was to see, so Kirk took a “Sunday drive” around the ship with his scooter on low gear, just relaxing and taking in the tour.  6 minutes and 8 seconds later, he surfaced with a huge smile on his face and had to fight through giggles to perform his recovery breaths!  Our protocols had proven their worth and over the past 10 days we successfully completed, to our knowledge, the first freedive expedition of the famous Ghost Fleet of the Truk Lagoon.


The wrecks of the Truk Lagoon offer a huge variety of options to explore an important part of WWII naval history.

We’re planning a return trip in January of 2018.  The exact dates are yet to be determined, but the details will be similar to the trip we just did.  Here’s a link to the details from this year’s trip:

There is a maximum capacity of 16 people on the Truk Master, so if you’re interested in joining us, just shoot us an email at to let us know and we’ll put you on the list to receive future updates and registration info.

Our group with the Captain and Crew of the Truk Master

For more information and links to the sites referenced above:


·        Operation Hailstone and Chuuk Lagoon




·        Technical Freediving



·        Master Liveaboard’s Truk Master



·        We’re planning a return trip in January of 2018.  The exact dates are yet to be determined, but the details will be similar to the trip we just did.  Here’s a link to the details from this yea’s trip:


There is a maximum capacity of 16 people on the Truk Master, so if you’re interested in joining us, just shoot us an email at to let us know and we’ll put you on the list to receive future updates and registration info.


·        Links to our equipment partners who helped make the 2017 Truk Technical Freediving Expedition possible:

o   Dive Xtras   

o   Light & Motion

o   Suunto          search/See-all-dive-products/

o   Pacific Pro Dive & Sea the World Travel