Finding the Wreck of the “Admiral Knight”
Professional archeologist and tech diver Ewan Anderson recounts the tale of finding the early 1900s steamship the Admiral Knight in British Columbia waters in the spring of 2020—a collaboration of the British Columbia Underwater Explorers (BCUE) and the Underwater Archaeological Society of British Columbia (UASBC). It’s a tribute to the power of “Citizen Science,” and the joys of diving with purpose. Here’s how they found it.
By Ewan Anderson
“Well… I might have a target for you,” read the fateful email that led to our search for the wreck of the early 1900s Admiral Knight steamship.
It was 2019, and Craig Lessels of the Canadian Hydrographic Service (CHS) had been reviewing multi-beam sonar bathymetry datasets — basically, maps of the seafloor — when he noticed a cluster of features lying on the otherwise sandy seafloor, east of Galiano Island in the Salish Sea off the west coast of Canada.
Thinking the Underwater Archaeological Society of British Columbia (UASBC) might be interested, he forwarded what he had found to UASBC Explorations Director Jacques Marc.
As it turned out, the UASBC had, since 2006, been looking near this location for the Admiral Knight, a steam-powered freighter that sank after an explosion in its engine caused a catastrophic fire on board.
The UASBC search began, as usual, with some serious background research. The research turned up a wealth of information about the vessel’s origins and destruction in 1919. Launched by the Westward Navigation Company of Seattle in 1916 as the Kuskokwim River, the 43 m/142 ft long wood hulled, diesel-engine powered vessel was built to provide freight service between Puget Sound and Alaska. It was re-powered with steam engines in 1917 and renamed the SS Portland, and then renamed the Admiral Knight in 1919 after purchase by Alaska Pacific Fisheries, who may have used it to supply their canneries in Alaska.
On July 26, 1919, a fire broke out in the Admiral Knight’s engine room while the freighter was underway from Seattle to Ketchikan. The crew of 21 barely made it off the ship before it was engulfed in flames; the last six men leaped off the foredeck onto a boat dispatched by the local steam ferry just in time to be saved. Three days later, mariners were still being warned of the burning hulk drifting between Vancouver and Vancouver Island, but there was no sign of the ship by July 30.
The Admiral Knight was forgotten until the late 1950s when a group of divers explored a site near Galiano Island where a local fisherman reported to have snagged his gear on a wreck. In an interview in 2006, one of the divers remembered seeing an intact wooden hull and some machinery matching the Admiral Knight’s description at depths of 55-64 m/180-220 ft; although this firsthand account came with the caveat that they were “narked out of their minds.” This general location became the focus of the UASBC’s field surveys over the next few years, including searches using towed side-scan sonar in 2006 and a multi-beam sonar survey by Parks Canada’s research vessel, the MV David Thompson. Those searches did not locate anything resembling the Admiral Knight wreck, and its location remained a mystery until CHS’s review of data from deeper water in 2019, just beyond the UASBC’s previous search areas.
The CHS target sits in 57 m/187 ft of water, which puts it beyond the range of the UASBC Explorations “regulars” group, some of whom have been exploring and documenting underwater maritime heritage sites in British Columbia and Alaska since the early ‘80s. As a UASBC Explorations regular myself — albeit with only 15 years’ worth of expeditions in my dive log — and member of British Columbia’s close-knit Global Underwater Explorers (GUE) technical diving community, Jacques turned the project over to me and wished me luck. I had been bothering Jacques for several years to give up his wish list of deeper shipwreck targets, and it appeared that this was my chance to prove that GUE tech divers on Vancouver Island could make a significant contribution to the underwater cultural heritage record on B.C.’s coast.
We were ready! In short order, I had a team of qualified and enthusiastic GUE divers, a dive boat, and a dive date in April 2020. And then we were interrupted by the pandemic. Organised diving took a big step back while everyone tried to figure out how to navigate a variety of restrictions and act responsibly in the face of this century’s biggest global health scare. Focus shifted to community-building through impromptu dives, and the big projects, like our plan to identify the Admiral Knight, took a back seat.
Dive boats available for projects around south Vancouver Island changed, too. GUE instructor evaluator and Vancouver Island resident Guy Shockey bought a boat, the Thermocline, brought it up to the island from Puget Sound, then learned how to drive it (possibly in that order). While the boat was still just a twinkle in Guy’s eye, he told me he hoped to make Thermocline a platform for divers to do world-class diving, but for that to happen it was up to the local GUE community to demonstrate that we had interesting project dives to do. He and I agreed that identifying the Admiral Knight fit the long-term community goals perfectly. Soon after the Thermocline arrived at its permanent home in Vancouver Island’s Maple Bay, Guy started referring to himself as “The Boat Driver,” so I knew he was seriously committed.
By early 2022, our diving activities on the west coast were back to their pre-pandemic norms, and the way seemed clear to dive the Admiral Knight. So, on a sunny weekend this past August, with water as calm as glass, I found myself dropping through the cool, emerald-green depths towards the bold future of underwater archaeology in my backyard.
Dropping down the shot line with me was Jason Cook, an instructor and fellow rebreather diver. As we descended, I had a head full of plans and checklists, and handfuls of equipment. Try as we might to keep things simple, we were determined to complete a minimum number of tasks and needed the gear to pull them off. In addition to our JJ-CCR rebreathers and bailout cylinders to do the dive, we had a full-frame camera and two pairs of large video lights to document the wreck (if it wasn’t just a pile of rocks we were dropping onto). Jason had a 120 m/400 ft reel in case The Boat Driver dropped the shot in the middle of nowhere and our identification dive turned into a search for, well, anything. I had an additional large surface marker buoy (SMB) stuffed in my left thigh pocket, which we planned to launch without a line attached to signal the next dive team that we’d found something worth diving. We each had a diver propulsion vehicle (DPV) to drag all this stuff around if the current picked up (strong currents are common in our region, but also highly localised, and nobody was sure when slack tide was at this new site).
The visibility on the descent was just over 20 m/60 ft, which is fantastic no matter where you are in the world. As we passed 40 m/130 a huge grey shape swam right in front of me — a shark! — no, just the biggest lingcod (Ophiodon elongatus) I had ever seen. As the monster fish disappeared, we hit a layer of low-visibility water hovering about 5 m/15 ft off the seafloor. It appeared we were going to be diving in the dark — and the cold, since it was also suddenly only 9° C/~48° F. Finally, the shot appeared below us, lying on a featureless, sandy plain. There wasn’t even a pile of rocks pretending to be a wreck in sight.
Like the optimist he is, Jason quickly got out his reel to tie-off and start a search. I, on the other hand, stared dejectedly into the gloom, where I could just make out some white blobs in the distance. But wait a second — the blobs must be plumose anemones (Metridium farcimen), and anemones must be attached to something! I got Jason’s attention with a flash of my light, and we headed off towards the anemones.
It turned out that our search for the wreck was brief — the anemones were only about 10 m/30 ft away, attached to a driveshaft just forward of a small steel propeller. It was a convenient place to tie off the reel, and an auspicious start to our dive. I deployed the SMB, which, unencumbered by a line attached to a spool, careened to the surface, and launched, like a small pink ballistic missile, out of the water beside the waiting Thermocline. The second dive team — Lee Critchley, Conor Collins, and Colin Miller — were into the water in moments to start their dive.
Back at the wreck site, Jason and I started the next phase of our dive: a visual survey of the site. Firing up the DPVs, we followed the driveshafts forward from the propeller. The shafts disappear under a jumble of machinery that will need a more thorough survey to sort through. The large water-tube boilers appeared next, standing upright on their fire-boxes about 2-3 m/6-10 ft proud of the seafloor. Patches of the relatively thin steel encasing the boilers had corroded away, revealing intricate tubing that was cutting-edge boiler technology in the early 20th century. Winches and engine parts formed another pile forward of the boilers, beyond which was the relatively featureless expanse of seabed corresponding to what was once the vessel’s hold. About a minute later, we rounded the forecastle which sat upright about 3 m/10 ft high, the foredeck winch still in its original position. We completed our circuit with a straight run back to the stern, spotting the second drive shaft and propeller.
As the second team arrived on the bottom, Jason and I lit up the wreck with our video lights. I wanted to document the visual survey we’d just completed, so I coordinated with Jason to do a re-run at slow speed. He led and illuminated the wreck, while I followed with the DPV-mounted camera and lights. Keeping Jason in frame made for a good scale reference as we slipped slowly past century-old rust and watchful fish. The end of our video captured the other team swimming around the boilers. Conor was taking still photos while the others inspected the machinery and puzzled out what they were looking at.
And just like that, it was time to go. Leaving the reel for the other team to collect, Jason and I headed back to the shot line and had the usual brief conversation confirming our decompression plan before leaving the bottom. The ascent took us back up to the relatively crystal-clear water above 45 m/150 ft. We crossed the thermocline around 15 m/50 ft and completed our deco in 18°C/64° F water and dappled green sunlight.
Back onboard the Thermocline, we all agreed that the first day of diving was a great success. We had identified a wreck and concluded that it was worth diving again; but was this definitely the wreck of the Admiral Knight? We thought so: it is a steam-powered, twin-screw vessel of the correct size. And we knew the burning hulk was seen by several witnesses drifting in the vicinity of our wreck site in late July 1919. More definitive evidence of the wreck’s identity lies in a closer inspection of the surviving equipment and the cargo. We surfaced with about 10 minutes of good-quality video and some still photos, which Jacques will want to review and comment on.
The two-hour sail back to the dock, and lunch at the marina pub gave us plenty of time to debrief and discuss the details of our dives. We sketched out the goals for diving the next day, and I included a somewhat ambitious list of items to measure and a plan to create a 3D model of the boilers.
Jason and I were back in the water 24 hours after our first dive on the wreck. The shot line had landed right behind the boilers, so we got to work immediately. This time, we planned to document the boilers using photogrammetry. Issues with camera float arms the previous day meant we were not able to carry as many big lights, so I had the camera while Jason handled most of the lighting.
The somewhat poor visibility and missing lighting (though we still had a lot of lights) meant we had to get relatively close to the wreck for well-lit photos. And since the boilers don’t cover a very large area, I decided to park the DPVs and kick. In hindsight, the DPVs might have made things easier, but I didn’t notice the current sweeping across the wreck until after the kicking started. I’m not beyond second-guessing myself underwater, but with only 30 minutes of bottom time to set-up and complete the photogrammetry, there wasn’t a lot of time to reorganise and restart the work. In the end, we managed to get about 470 reasonable photos for our modelling project.
The second dive team, Guy and Jim Dixon, arrived on the wreck a few minutes after Jason and I started taking photos. Guy and Jim had the straightforward task of just enjoying the dive. This seemingly simple job is a common assignment on UASBC dives: divers who are unencumbered with cameras, lights, measuring tapes, and other documentation equipment are free to explore and are likely to notice important features that busy diver-photographers might miss. This team spent some time inspecting two “block” features that I had noticed the previous day; sitting forward of the engines and boilers, the blocks could have been the remnants of the vessel’s cargo, which would be an unusual find because we don’t often see intact cargo on our wrecks. We didn’t manage to solve the mystery on this expedition, and even with Guy and Jim offering detailed descriptions, we’re all still scratching our heads.
Although there were only a handful of divers who made it down into the wreck in August, dozens of people have contributed their time and energy over the last decade and a half to making these successful dives possible. To dive into the unknown just to see what’s there is one thing, but to dive with purpose and come back with valuable information requires dedicated research and planning. Credit for our success (and the pressure to succeed!) in search for the Admiral Knight is largely due to Jacques Marc and other researchers at the UASBC who laid the groundwork for the project.
There is much more to come. We’ve proven that we can add deeper sites to the list of the UASBC’s potential expeditions. Jacques and other UASBC volunteers are turning to the archives to find more targets. By extending the range of what is possible for the local community, we also open the door to exploring deeper into history. Indigenous peoples have lived around the Salish Sea since time immemorial, as indigenous elders and cultural leaders say, and their cultural inheritance includes documented sites spanning the last 14,000 years. The connection Salish peoples have with the sea around us is undeniable, yet tangible underwater heritage sites other than shipwrecks have barely been explored.
As for the Admiral Knight, any uncertainty about the wreck’s identity may be beside the point. The wreck still makes for a great dive, and although it is relatively deep for most divers, many in our local dive community are qualified – or will be soon – to dive it. It’s worth the effort just to see the intact boilers and the entire vessel’s contents laid out on the seafloor, just as they were 103 years ago. The intact sections of wreck and potential cargo provide opportunities for further study and research as well.
See companion stories:
Building Community Through Project Diving By Guy Shockey
Introducing GUE’s New Project Diver Program By Francesco Cameli
InDEPTH: How to Become an Explorer: Passion, Partnership, and Exploration
Underwater Archaeological Society of British Columbia
Marc, Jacques and Warren Oliver Bush (2021) Historic Shipwrecks of the Southern Gulf Islands of British Columbia. Underwater Archaeological Society of British Columbia, Vancouver, B.C.
Ewan Anderson is a professional archaeologist whose work focuses on assessing and mitigating development construction impacts to cultural heritage sites in British Columbia. A consultant for all levels of government, a variety of industries and Indigenous communities, his expertise is in cultural heritage law, cutting edge archaeological methods and Indigenous peoples’ relationships with archaeology and those who practise it.
Ewan is passionate about diving – especially when combined with underwater cultural heritage projects. He is a GUE certified JJ-CCR diver and IANTD certified cave diver. His diving has taken him around the world, even though everything he needs – from wrecks to caves – can be found within a few hours of his home in Victoria, on Vancouver Island.
His professional work and diving almost never mix, for which he is often thankful. Ewan pursues his interests in underwater photography, underwater photogrammetry, and advocating for conservation of marine environments and underwater heritage, free from the yoke of capitalist overlords. He is a regular volunteer on Underwater Archaeological Society of BC expeditions and has served on the Society’s board of directors since 2018.
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!
By Ashley Stewart. Images courtesy of Simon Mitchell unless noted.
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.
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.
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.
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.
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.
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.
“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.
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.”
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.
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.
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.
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.
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.
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.
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: email@example.com.
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