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Shitwrecks

We teamed up with some potty-minded wreckers to explore the poop decks of shipwrecks around the world. Water sports anyone? We offer these heady bits.

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In our ongoing search for unusual images, InDepth may have unwittingly uncovered a closeted water-based fetish among some of the who’s who of wreck diving. I shit you not. 

The fit first hit the shan when we reached out to renowned British wrecker and photographer Leigh Bishop to see if he had any pictures of sunken shipwreck heads. Bishop was a bit dodgy in his email reply. “Just out of curiosity, who else have you asked? Has anyone actually come back and said they have photos of heads?” 

Hmm…

We responded in the affirmative; hyperbaric doc cum wrecker Andrew Fock had indeed sent us a snap depicting a gaggle of sunken thrones from the British warship HMS Hermes. Bishop immediately let loose a missive as if he had been holding it back. “OK,” he replied. “I was just wondering if I wasn’t the ONLY weirdo to have shots of toilets. I do have some, bear with me.” Bishop then dumped NINE images in our box in less time than it took to say “Holy crapper!”  

Once we had Fockie and Bishop in the can, the others followed quickly without raising a stink. Crappy photos started to flow in. We had hit the thunderbox! In fact, shipwreck historian and producer Richie Kohler was one of the few who was obstructive. After complaining about not having a pot to piss in, the inveterate wrecker spilled the beans, “No crappy pix here,” he wrote. “You’re shit outta luck and gonna have to head elsewhere to find a John. Sorry for my potty-mouth. Toodle Loo.” Now that’s a “Dear John” letter!

Our efforts were deeply rewarded when we learned that our late dear brother, wreck diving pioneer Bart P. Malone (1946-2017) had a thing for honey buckets. A sweet guy, to be sure. Accordingly, we were able to extend a short but heady tribute to the legendary old-school wrecker, one that he would surely appreciate, as you will soon learn. Thank you Rusty Cassway and Becca Boring for this offering.

The bottom line? You be the judge. We think this was some pretty deep shit.—M2

Thank you to these courageous heady wreckers for their pics of pots and more; Aron Arngrimssοn, Leigh Bishop, Becca Boring, Jason Brown, Rusty Cassway , Andrew Fock, Melissa Foo, Gary Gentile, Jesper Kjøller, Chris Kohl, Richie Kohler, Nicolas Lurot, Beto Nava, Pete Mesley, Roger Montero, Erik Petkovic, Becky Kagan Schott, and Tamara Thomsen. Special thanks to John Fitzgerald and Yuko Takegoshi for inspiring the idea.

Header image: A bevy of toilets from the Cypriot cargo ship Yolanda which grounded on a reef at Ras Muhammed in 1980, spilling her cargo. Image from Alamy Ltd.

HMS Hermes

The HMS Hermes was the world’s first purpose built Air Craft Carrier. It was commissioned by the British Royal Navy in 1923 and sunk by the Japanese on April 9, 1942 with the loss of 307 of its crew. Depth (toilets): 44m/145ft. Photo (2010) by Andrew Fock.
Photo by Pete Mesley.

HMNZS Canterbury

HMNZS Canterbury, A New Zealand frigate scuttled in Bay of Islands, New Zealand in 2007. Depth: 31m/103ft. Photos by Pete Mesley.

MS Mikhail Lermontov

MS Mikhail Lermontov, was an Russian Ocean Liner that collided with rocks near Port Gore, New Zealand and sank in 1986. Depth: 28m/94ft. Photos by Pete Mesley.

SV Kingsbridge 

The SV Kingsbridge was an iron hulled clipper ship that sunk after colliding with the sailing ship Candahar with the loss of 15 lives. Depth 90m/295 ft. Photo by Leigh Bishop.

SV Avalanche

SV Avalanche was a three-masted iron sailing ship that sunk in the English Channel in 1877 after colliding with the sailing ship SV Forest, which also sank. Lives lost: 106. Depth: 52m/171ft. Photo by Leigh Bishop.

The SS Egypt

A P&O Liner carrying gold & silver cargo. She sank after a collision in the Celtic Sea. Depth: 127m/417ft. Photo by Leigh Bishop.

Unidentified Paddle Steamer

North Sea. Depth: 50m/164ft. Photo by Leigh Bishop.

SS Tuscania 

The SS Tuscania was a luxury liner that was torpedoed and sunk in 1918 in the Northern Channel between Scotland and Ireland by German U-boat UB-77 while transporting American troops to Europe with the loss of 210 lives. Depth: 102m/335ft. Photo by Leigh Bishop.

SS Justicia

The SS Justiçia was British Troopship that was torpedoed and sunk during WWI near Skerryvore, Scottland. Depth: 70m/229ft. Photo by Leigh Bishop.

Kensho Maru

The Kensho Maru was a passenger cargo ship sunk in Truk Lagoon during Operation Hailstorm in 1944. Depth: 36m/118ftPhoto by Leigh Bishop.

The Oite Destroyer

The Oite Destroyer was a Kamikaze class destroyer sunk in 1944 in Truk Lagoon. Depth: 66m/217ft. Photo by Leigh Bishop.

Katsurigusan

Katsurigusan Maru was a cargo ship sunk by a Japanese mine in Truk Lagoon in 1944, and is Truk’s deepest shipwreck. Depth: 70m/229ft. Photo by Leigh Bishop.

MS King Cruiser

MS King Cruiser was a car ferry that sank off the West Coast of Southern Thailand on 4 May 1997.  Depth: 24 m/80 f. Photos by Nico Lurot.

SMS Cōln

The SMS Cōln was a light German cruiser scuttled in Scapa Flow at the end of WWI. Depth: 36m/118ft. Photo by Jason Brown, bardophotographic.com


Aikoku Maru

The Aikoku Maru was an armed merchant cruiser of the Imperial Japanese Navy in World War II. The ship entered service in 1940, and was sunk in February 1944 during Operation Hailstone. Photo by the Dirty Dozen Expeditions.
Photo by Pete Mesley.

Yolanda

Yolanda was a Cypriot cargo ship built in 1964. She was carrying a load of porcelain toilets and bathtubs when she was grounded on a reef at Ras Muhammed in 1980, spilling her cargo. She subsequently slipped off the reef in deep water in 1985 during a storm. Depth: 15m/49 ft. Photos by Jesper Kjøller.

C53 Felipe Xicotencatl

Roger Montero—the “Mayan Diver”—perched on the throne of the C53 Felipe Xicotencatla US Built Admirable-Class minesweeper that was decommissioned in 1999, donated to the Cozumel underwater park and sunk that same year. Depth: 15m/49ft. Photo courtesy of Roger Montero.

Added April 5, 2022—Some recent poop on the RUBY E: “Lonely Toilet

SS Andrea Doria

A head on the iconic SS Andrea Doria which sank in July 1956 after a collision with the SS Stockholm off Nantucket Island, Massachusetts, killing 51 people.  Depth (toilet): 58m/190 ft. Photo by Gary Gentile.

USS Wilkes-Barre

USS Wilkes-Barre was a Cleveland-class light cruiser of the US Navy that served during the last year of World War II and was skuttled in 1972. She served as the training wreck for Capt. Billy Deans’ Key West Divers mixed gas classes in the 1990s. Depth: 64m/210 ft. Photo by Gary Gentile.

The SS America

The America was a packet boat transporting passengers, mail, and packages between settlements Isle Royale National Park, Lake Superior, US. Built in 1898, the America sank in Washington Harbor off the shore of Isle Royale in 1928, where the hull still remains. Depth: 24m/80ft. Photo by Tamara Thomsen.

The SS Monarch

The SS Monarch was a passenger-package freighter built in 1890 that operated on the Great Lakes. She was sunk off the shore of Isle Royale in Lake Superior in 1906 and the remains of her wreck and cargo are still on the lake bottom.  Depth: 24m/80ft. Photo by Tamara Thomson.

SS Daniel J Morrell

Rebreather diver explores the captain’s quarters inside the SS Daniel J Morrell, a Great Lakes freighter that broke up in a strong storm on Lake Huron in 1966, taking with it 28 of her 29 crewmen. Depth: 51m/165ft. Photo by Becky Kagan Schott. 

The AA Parker

The AA Parker was a wooden steamship that sank in 1903 during a storm in lake Superior near Grand Marias, Michigan. Notice the bell behind the toilet. Depth: 64m/210ft. Photo by Becky Kagan Schott.

RH Rae

PThe “RH Rae” was a three-masted bark that capsized during a white squall on Lake Ontario in 1958 near Point Traverse. The wreck was explored by the Cousteau in 1980, the only time they ever visited the Great Lakes. Unfortunately, they lost a diver at this site—the only time they had a diving fatality. Depth: 32m/105ft. Photo by Chris Kohl

Shinkoku Maru

The Shinkoku Maru was a Japanese oil tanker that was sunk in Truk Lagoon in 1944 during Operation Hailstone. Below Rusty Cassway pours Bart P. Malone’s  ashes into the Shinkoku Maru head in 2019. Photos by Becca Boring 

Bart P. Malone (1946-2017)

Bart Malone post dive August 2016. Photo by Rusty Cassway

Diving legend Bart P. Malone, who passed away in December, 2017, was an avid collector of shipwreck china. (He was also the co-founder of The Gas Station, the first technical mixed gas station in the Northeast US.) Bart collected ship line china from many of the classic wrecks including the Andrea Doria, SS Carolina and the Empress of Ireland. However, to Bart the quintessential piece of china to obtain was a ships head or toilet.  It was like a giant ceramic bowl. Just bigger.  Bart did this “tongue in cheek”, because as many who knew Bart were aware, he liked to spend a lot of time in the dive boat head prior to and after dives.—Rusty Cassway

Ed. Note: Shipwrecks that have been underwater for more than 100 years, including their sunken heads, are protected by the United Nations Educational, Scientific and Cultural Organization (UNESCO) Convention on the Protection of the Underwater Cultural Heritage. Divers are requested not to disturb or remove artifacts from these wrecks. Thank you Rupert Simon from Finland, for bringing this to our attention.



Cave

N=1: The Inside Story of the First-Ever Hydrogen CCR dive

This Valentine’s Day, Dr. Richard Harris, aka ‘Dr. Harry,’ and the Wetmules made the first reported hydrogen (H2) rebreather dive to a depth of 230m/751 ft, in The Pearse Resurgence, New Zealand. The 13 hour dive, which was nearly two years in planning, was a field test to determine the efficacy of using hydrogen to improve safety and performance on über-deep tech dives. Harris’s dive was the deepest “bounce” dive in approximately 54 experimental H2 dives—the majority SAT dives—that have been conducted over the last 80 years by military, commercial and, yes, a group of technical divers. Now in this first published account, InDEPTH editor Ashley Stewart details the inside story behind the dive, a dive that will arguably be remembered 100 years from now!

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By Ashley Stewart. Images courtesy of Simon Mitchell unless noted.

Richard ‘Harry’ Harris embarking on the first hydrogen rebreather dive on 14 FEB 2023.

On March 11, a little more than three weeks after completing what is believed to be the first-ever rebreather dive with hydrogen as a diluent gas, Dr. Richard “Harry” Harris convened the group of scientists and researchers who had spent years helping to plan the attempt.

He started with an apology. “All of you had the sense that you were party to this crime, either knowingly or suspecting that you were complicit in this criminal activity,” Harris, an Australian anesthesiologist and diver known for his role in the Tham Luang Cave rescue, told the group.

The apology came because the dive was dangerous—not just to Harris who was risking his life, but for the people who supported him were risking a hit to their reputations and worried their friend may not return home. Harris and his team put it all on the line to develop a new technology to enable exploration at greater depths.

A significant challenge to deep diving is an increased work of breathing and CO2 buildup as breathing gas becomes more dense at greater depths. This can not only culminate in fatal respiratory failure but also increases the risk of practically everything else divers want to avoid, like inert gas narcosis and oxygen toxicity. For this reason, helium is favored by divers for its low density and non-narcotic effect. However, at such great depths, helium increases the risk of tremors and seizures from High Pressure Nervous Syndrome (HPNS). This can be ameliorated by keeping a small amount of narcotic nitrogen in the mix. The problem is that even small amounts of nitrogen makes the mix too dense past 250 meters.

Harris’s experiment would determine if divers can turn to an even lighter gas: Hydrogen, the lightest in the universe. Hydrogen is about half the density of helium. It’s also slightly narcotic and hence thought to ameliorate HPNS, thus allowing elimination of nitrogen from the mix. 

Gas density is NOT a diver’s friend. Increased gas density above 6.1 g/l increases a diver’s risk of having an “event” during a dive. You do NOT want an eventful dive! Chart courtesy of John Clarke.

The addition of hydrogen into a breathing gas, however, comes with one small technical uncertainty—the extremely explosive nature of hydrogen. History confirmed this reality with the 1937 Hindenburg disaster in which the hydrogen-filled dirigible airship burst into flames. As Harris tells it, he set out to dive hydrogen in his diluent gas while avoiding the nickname “Hindenburg Harry.”

Hydrogen in the Mix

Why would anyone attempt to breathe hydrogen? Harris and his colleagues have spent more than a decade and a half exploring the Pearse Resurgence cave system in New Zealand. This extremely challenging, cold water cave system (water temperature is 6ºC/43ºF) has been explored by Harris and his team, who call themselves the Wetmules, to a maximum depth of 245 meters/803 feet in 2020. Their gas density at depth was 7.2 g/l, significantly above the recommended hard ceiling of less than 6.2 g/l.

Harry’s dive profile of their 245m dive at the Pearse Resurgence in 2020. The gas density is in the Red Zone!

Diving past this point introduces increased risks, not only of CO2 buildup, but narcosis, decompression sickness, HPNS, cold breathing gas, having adequate gas supply or bailout, and isobaric counter diffusion (ICD) in which different gasses diffuse into and out of tissues after a gas switch causing bubble formation and related symptoms, cold breathing gas, and having adequate gas supply or bailout. 

Sheck Exley at Manté

Divers have been examining hydrogen as a breathing gas for decades. The Swedish Navy was the first to experiment with hydrogen as a possible deep diving gas during World War II. The U.S. Navy in a 1965 paper proposed replacing helium with hydrogen due to projected helium scarcity. Later, beginning in 1991, researchers at the Naval Medical Research Institute (NMRI) in Bethesda, Maryland spent a decade studying hydrogen’s potential physiological impacts and biochemical decompression. French commercial diving contractor Comex (Compagnie maritime d’expertises) launched its hydrogen program in 1982, and the Undersea Hyperbaric Medical Society (UHMS) held a workshop “Hydrogen as a Diving Gas,” in 1987.

Even technical divers considered hydrogen. Legendary cave explorer Sheck Exley considered hydrogen in the early 1990s to mitigate HPNS symptoms, which are ultimately believed to have contributed to Exley’s death at Zacatón in 1994. Nearly all of the experimental hydrogen work up until this point used surface-supplied systems and saturation diving versus self-contained diving, and none of it, as far as we know, has been done with a rebreather.

Cave explorer Craig Challen

The primary objective of Harris’ hydrogen experiment was to address the issue of increased work of breathing. Harris’s team had previously encountered CO2 incidents at the Pearse Resurgence. In one incident, while at 194 meters/636 feet, explorer Craig Challen—Harris’s primary dive buddy since 2006—lost buoyancy but was unable to find his buoyancy compensating button quickly. He kicked up a couple of times to stop his descent and immediately got a CO2 hit. Challen was able to grab the wall, calm down, slow his breathing, and survive. Based on such incidents, it’s clear to the team that they have reached the limits of the gas. “I feel we are on the knife edge all the time,” Harris said, in terms of physiology and equipment.

While hydrogen in the diluent breathing mix was expected to address increased work of breathing, the rest of the issues associated with deep diving were “major unknowns,” and some (such as respiratory heat loss) were potentially even made worse by hydrogen.

“At what depth do the risks of introducing this new technology outweigh the risks of carrying on with trimix?” Harris said. “That’s a very difficult question to answer. At some point we are going to have to consider different technologies and, at this point, hydrogen is perhaps the only one available to us.”

H2 Working Group

In 2021, the year after Harris completed his deepest dive at the Pearse Resurgence, InDepth editor-in-chief Michael Menduno was taking a technical diving class and reading about the government looking at hydrogen as a diving gas again. “Technical divers should be at the table,” Menduno said he thought to himself at the time, “our divers are as good as anybody’s.” He called John Clarke, who had spent 27 years as scientific director of the U.S. Navy Experimental Diving Unit (NEDU), and discussed setting up a working group. Menduno’s next call was to Harris, who had shared his troubles with gas density at the Pearse Resurgence. Harris had also, separately, been thinking about hydrogen.

The so-called H2 working group met for the first time in May 2021 and included many of the top minds in diving medicine and research, including Clarke, NEDU’s David Doolette and Greg Murphy, research physiologist Susan Kayar who headed up the US Navy’s hydrogen research at the Naval Medical Research Institute (NAMRI), along with her former graduate student Andreas Fahlman. There was diving engineer Åke Larsson who had hydrogen diving experience, deep-diving legend Nuno Gomes, decompression engineer JP Imbert who had been involved in COMEX’s Hydrogen diving program, and anesthesiologist and diving physician Simon Mitchell. The group was later joined by Vince Ferris, a diving hardware specialist from the U.S. Navy, and explorer and engineer Dr. Bill Stone, founder of Stone Aerospace.

The working group met regularly with the goal of figuring out how one might possibly operationalize hydrogen for a deep technical dive using the Resurgence as an example. During one of their meetings, Clark used a breathing system simulator built for the Navy to predict how hydrogen would affect gas density in a closed circuit rebreather at depths to 300 meters/984 feet.

To Doolette, who has known Harris for decades and supervised his Diploma of Diving Medicine project in 2001, it was immediately clear this was not a hypothetical discussion. “Unlike some of the scientists, I was under no illusion that the question before the working group was fiction, I knew that Harry was likely to try a H2 technical dive in the Pearse Resurgence,” said Doolette, a cave explorer in his own right, who has laid line in the Resurgence. 

Diving physiologist and explorer David Doolette in northwest Florida. Photo courtesy of D. Doolette.

By fall of 2022, it was clear to many in the group that Harris was going to attempt the dive. The group had mixed feelings ranging from cautious optimism to comments like, “My friend is going to die.”

Doolette was concerned Harris and Challen would not survive the dive due to either ignition of hydrogen—in the worst case, inside the rebreather at depth—or a serious adverse response to respiratory heat loss (the latter was especially if Harris attempted diving beyond 245 meters/803 feet as he had originally planned) he said. “I have known Harry for longer than most in the group. I encouraged him to take up cave diving, so I felt a personal responsibility toward him,” Doolette said. “I have a lot of experience in operationalizing new diving technology. My goal was, if unable to discourage him, to force him to focus on the important issues.”

Leading up to the dive, Menduno scheduled Harris to give the banquet talk about the expedition at the Rebreather Forum 4 industry meeting in April. The outcome of the dive, of course, was uncertain, and the two had to make an alternate plan in the event that Harris did not return. “We had to say we were going to talk about your dive one way or another,” Menduno said. “If you don’t make it back, Simon Mitchell is going to have to give a presentation about what went wrong. Harry made some typical Harry joke like, ‘Well, as long as you don’t stop talking about me.’” Harris’s lighthearted tone betrays how seriously he took the dive and its preparation, people close to him said.

While no one involved was taking as big a risk as Harris and Challen, they were risking a hit to their professional reputations by being associated with a controversial dive, especially in the event of a tragic outcome.

“At heart, I’m an explorer, and that was pure exploration,” Mitchell, who was the diving supervisor on Harry’s dive, said when asked why he would take such a risk. “Exploration in the sense that we were pioneering a technique that hadn’t been used for quite some time and never in technical diving, not deep technical diving.” He also emphatically added, “I was more worried about my mate dying than about my professional reputation.”

Later, in planning Harris’s trip to the RF4 event, Menduno had occasion to speak to Harris’s wife, Fiona who brought up the dive. 

Wetmules waiting for Harry and Craig to return from their dive.

“She said to me ‘I hope Harry is going to be OK’,” Menduno said. “I had no idea how much Harry told her, what she knew and didn’t know. All I could say was he’s got the best people in the world on his team, and if anybody can do it, he can.”

“We all held our breath and waited,” Menduno said.

‘Hydrogen Trials’ at Harry’s House

Ahead of the dive, Harris was preparing at home. The first thing Harris said he had to get his head around was—no surprise—the risk of explosion, and how to manage the gas to mitigate that risk. The potential source of explosion that Harry was most concerned with was static ignition within the CCR itself, plus other potential ignition sources like electronics, the solenoid, and adiabatic heating. Industrial literature—or “sober reading” as Harris calls it—suggested that the tiny amount of static necessary to initiate a spark to ignite hydrogen is .017 mJ, 400 times less than the smallest static spark you can feel with your fingertips and several hundred times less than required to ignite gasoline. “It ain’t much, in other words,” Harris said, noting that counterlung fabric rubbing against itself could generate just such a spark.

Don’t try this at home kids. Photo courtesy of Richard Harris.

Ultimately, Harris came across research that suggested that static decreases with humidity. “I started to feel like there was no source of ignition inside a rebreather, but then again I said to myself, ‘Harry you only need to be wrong once’.”

The other concern was whether he could actually fill hydrogen safely while decanting, or filling one tank from another at the same pressure, and boosting the gas to reach higher pressures.

“I decided there is only one way to actually resolve this and that is to retire to the shed, order a sneaky bottle of hydrogen, and without telling my wife what was going on down the back of the house, start to actually have a bit of a play with this,” Harris said.

First Harris had to make his own DIN fitting (though not out of the ordinary for the anesthesiologist who built and tested his own rebreather before buying a commercial one in 2002) to decant the gas. Next he took his dual Megalodon rebreather with 100% hydrogen in one diluent cylinder and 100% oxygen in the other to the “test bed” in his backyard—his pool—and started to introduce hydrogen into his rebreather. 

“Putting an explosive device into water was perhaps not the most logical approach because it becomes more like a depth charge than a bomb, but I thought, ‘Well, at least it might contain the blast somehow into the pool.’ I knew if I broke the back windows in the house or worse, my life wouldn’t be at risk just from the hydrogen. There would be bigger trouble afoot,” Harris said. “I left the lid of the rebreather unclipped in the vain hope it would spare me and the pool and the dog, who was helping with this experiment.”

Dual Megalodon rebreathers connected via their BOVs. Photo courtesy of R. Harris.

He pressed the button of the Automatic Diluent Valve (ADV) on his rebreather, introducing hydrogen to the loop, and finally activated the solenoid before he started breathing from it. The first breaths were pleasant, he said. “It did feel very light and very slippery, and the hydrogen voice is even sillier than the helium voice, as you would expect,” he said. “I don’t want people to rush away thinking this is a safe and sensible thing to do. I’m under no illusions I’ve produced any evidence for you to see, but this is an honest account of the hydrogen trials at my house.”

The unit had not exploded with a fill of oxygen from zero to 70%, and very low humidity. “Harry, dog, and CCR survive,” as Harry wrote in his report of the trials. “Nothing bad had happened, so it was reasonable to move to the next step,” he said.

A gear intensive expedition that required 10 helicopter trips to ferry in all of the equipment.

The Expedition

Harris, Challen, and other members of the Wetmules, arrived at the site of the Pearse Resurgence on New Zealand’s south island in February 2023. The cave system is so remote they needed around 10 helicopter trips to transport the team and all of its equipment. Mitchell, the diving physician, ran surface operations with “mixed feelings,” as Harris put it.

The group stayed for two weeks at a campsite, complete with a gas-mixing station, an electronics shelter for charging gear, and a “big green army tent where we meet and drink a lot of coffee and try and put off going back into the water each day,” Harris said.

Wetmules camp along the river.

The expedition was plagued with an unheard of number of problems, Harris said, “Every time we got in the water, something popped or blew up or failed.” The campsite is where Harris boosted hydrogen for the first time, from 100 to 150 bar. He flushed the booster and all the whips with hydrogen prior to boosting to make sure no oxygen was left in the system, but it was an anxious moment. 

On dive day, Harris and Challen set out on what would be a 13 hour dive to 230 meters/754 feet—a “comfortable depth,” as Harris put it. Due to some problems during the expedition, it was decided that Harry would dive hydrogen, while Craig would dive trimix. At 200 meters/656 feet depth, Harris pivoted the switch block to introduce hydrogen into the loop. “The first cautious sip of hydrogen just to activate the ADV was satisfying,” he said. Gas density was not subjectively improved, but Harris noticed an obvious benefit—the HPNS-induced hand tremors he typically experienced after 180 meters/590 feet disappeared. Harris kept his setpoint at .7 during the descent and working portion of the dive, careful not to reach a fraction of oxygen above 4% which would make the mix explosive, and proceeded to the 230-meter test depth. 

Wetmules camp chat.
Wetmules—Back row (left to right) Simon Mitchell, Dave Apperley, Craig Challen, Richard Harris, Dave Hurst. Front row (left to right) John Dalla-Zuanna, Ken Smith, Martyn Griffiths (with Colin, the team’s bowling ball mascot) and Luke Nelson.
Harry and Craig suiting up for the dive.
Harry’s secret sauce. Image by Martyn Griffiths
The entrance to the Pearse Resurgence
The 17 meter habitat.
Harry with Dual Megalodon and Seacraft scooter at the 17 meter habitat.

After completing their time at 230 meters, the team began their ascent. Harry shut off the hydrogen feed to the active loop of his dual Megalodon rebreather back at 200 meters, and then conducted a diluent flush every 10 meters/33 feet to remove the hydrogen from the loop until reaching 150 meters/492 feet. At that point, Harris boosted his PO2 to 1.3 from his set point of 0.7 (Challen remained at 1.3 throughout the dive), and they continued their ascent decompressing on a trimix (O2, He, N2) schedule, treating hydrogen as if it were helium. The complete technical details of the dive will be published in a forthcoming paper in the Diving and Hyperbaric Medicine Journal.

Harry arrives at the surface following his hydrogen dive.

As soon as the team were helicoptered back to civilization, Harry called Michael from the road. “Michael, we did it!,” Harris said.

“Harry, you’re alive!,” Menduno responded.

N=1

At that March meeting with the H2 working group, Harris presented his findings from the dive. “I’m not sure what to conclude to a highly scientific, analytical, and evidence-based audience like yourselves,” he told the group. “Conclusions: N=1,” meaning it had been successful one time.

Doolette, who had been the most vocal in the group about his concerns, suggested Harris could add to his conclusions “the probability of survival is greater than zero.” Doolette, whom Mitchell contacted as soon as they reached civilization, said he “was relieved to hear that Harry survived this test dive” but remains disappointed with some aspects of the experiment, and concerned about possible future attempts. “For instance, I imagine among the engineers he consulted would have been someone with the ability and resources to do a computational fluid dynamic analysis of the Megalodon rebreather to establish the ignition risk, but instead Harry filled his rebreather up with hydrogen in his backyard.”

Overall, Harris said his findings are that hydrogen can be handled and boosted, hydrogen and CCR diving are compatible, a strategy to introduce hydrogen on descent was successful, a decompression dive was successful, a low setpoint at depth did not practically affect total dive time, strategy to reintroduce a high PO2 on ascent was successful, and HPNS and narcotic impacts were subjectively favorable.

“In introducing hydrogen we have addressed the issue of gas density, but we certainly have not established it is safe to use in terms of explosion risk, decompression of the thermal hazards,” Harris said.

Among his conclusions, Harris pointed out that he also managed to evade the nickname “Hindenburg Harry.” “Fortunately that was avoided,” he said, “but remains an ever-present risk.”

The Future of H2

Harris warns not to read too much into what his team achieved—a single data point that should in no way encourage others to repeat the dive. “David Doolette’s comment should be heeded,” Harris said. “All we have shown is that we got away with it on one occasion.”

Provided it can be safely proven and built upon, Harris said he thinks of his hydrogen dive as a window into the future that would enable tech divers to continue exploring into the 250 to 350 meter/820 to 1148 feet range. “Imagine the wrecks and caves that lay unvisited around the planet,” Harris said.

DIVE DEEPER

YouTube: Wetmules 245m Cave Dive in the Pearse Resurgence, New Zealand (2020)

InDEPTH: Hydrogen, At Last by Michael Menduno

InDEPTH: Density Discords: Understanding and Applying Gas Density Research by Reilly Fogarty

InDEPTH: Playing with Fire: Hydrogen as a Diving Gas by Reilly Fogarty

InDEPTH: High Pressure Problems on Über-Deep Dives: Dealing with HPNS by Reilly Fogarty

InDEPTH: The Case for Biochemical Decompression by Susan Kayar

John Clarke Online: Hydrogen Diving: The Good, The Bad, the Ugly (2021)

InDEPTH: Diving Beyond 250 Meters: The Deepest Cave Dives Today Compared to the Nineties by Michael Menduno and Nuno Gomes.

Undersea Hyperbaric Medical Society: Hydrogen as a Diving Gas: Proceedings of the 33rd UHMS Workshop Wilmington, North Carolina USA (February 1987)

InDepth Managing Editor Ashley Stewart is a Seattle-based journalist and tech diver. Ashley started diving with Global Underwater Explorers and writing for InDepth in 2021. She is a GUE Tech 2 and CCR1 diver and on her way to becoming an instructor. In her day job, Ashley is an investigative journalist reporting on technology companies. She can be reached at: ashley@gue.com.

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