In the 1960s the US Navy developed three undersea habitats, in order to experiment with saturation diving and to explore the possibility of humans living on the ocean floor. Of necessity, any group of people engaged in this pursuit would be separated from life on the surface, in some cases by days or weeks of decompression obligations. SEALAB I, II and II were progressively deeper and more complex habitats. Developing them was a technical challenge that led to many advances that we benefit from today. The experiments also provided an opportunity to study the psychological and physiological effects of isolation, and of long periods of breathing mixed gases under pressure.
The SEALAB experiments took place during the same era as the efforts by NASA to put a person on the moon, and received far less attention. Jacques Cousteau was interested in the project, and himself experimented with underwater habitats called ConShelf I, II and II. These habitats were far better publicised than the US Navy’s efforts, even though their aims were more modest.
Author Ben Hellwarth does not confine his attention to the habitats, but also provides a fairly detailed history of decompression theory and diving history. Like Neutral Buoyancy, SEALAB might provide a relatively painless introduction to dive theory for Divemaster candidates. In fact, this book reads like a thriller at times! Some photographs from the SEALAB projects are available on the US Navy website, and in this slideshow. To our modern eyes, the clunky and primitive appearance of some of the gear is a reminder of how pioneering the now 60 year old work to allow humans to live and work in the sea was.
If you’re interested in the history of saturation diving, I recommend this article, which covers some of the ground that Hellwarth does in SEALAB. If you want to see it in action, check out Pioneer (fictional movie based on actual events) or the series Deep Sea Salvage. You should also check out this article by Hellwarth, entitled The Other Final Frontier, and this podcast/radio show. If you are EXTREMELY interested in this subject but don’t want to read a book, try out this hour-long lecture video by Ben Hellwarth.
Yesterday I told you about a dive on Doodles, a reef in southern Mozambique, during our trip to Ponta do Ouro last month. Doodles has a maximum depth of about 14 metres. After forty five minutes’ dive time, my Suunto D6 began to register extreme depths (89 metres maximum), and to give various instructions about decompression ceilings and times, accompanied by strident warnings about exceeding my PPO2.
Suunto D6 after missed decompression
While annoying and potentially dangerous to lose the services of my dive computer mid-dive, it was also an excellent learning opportunity. Because I usually try quite hard to be safe and not to upset my computer, and dive within the conservative, recreational limits that I am trained for, I never get to see any of this behaviour from the instrument. (Fortunately the dive was shallow and I still had plenty of no-decompression time left so it was far from an emergency situation.)
After the dive, I soaked the computer in warm fresh water, and it gradually came out of dive mode over a period of about ninety minutes. During the course of this simulated ascent, the required decompression times and depths calculated by the algorithm were not adhered to, so the computer entered an error mode, which, according to the manual, indicates that “the risk of DCI has greatly increased.” (In fact, from all the beeping and flashing, I suspect the computer thought I was dead or close to it.) This error mode does two things: it disables the dive planning capabilities of the computer, and it locks you out of dive mode for 48 hours.
The D6 in gauge mode
I had never gotten the computer into this state before, so I was keen to see how it behaved when I took it on a dive in error mode. You can see in the photo above that I am wearing Tony’s Mares Nemo Wide (aka the flatscreen TV) to give me actual information about my no-decompression time, depth and dive time, but I took my D6 along for the ride. It is in gauge mode; this means it gives you only measurements, and is the setting a free diver might use.
The measurements available in gauge mode are: depth (18.4 metres in the photo above), the maximum depth you’ve been to on this dive (19.9 metres), an elapsed dive time (17 minutes), and water temperature (not shown) but it refuses to calculate a no-decompression limit for you. This would usually appear where the Er appears in the picture above.
Depth profile (with warnings)
For your enjoyment, here’s another screen shot of the dive profile from MacDive, with the warnings expanded. Click on the image to see it full size. It is clear that the first warning beeps I heard during the dive were because of elevated PPO2 levels. At 89 metres the device immediately put me in deco, and then as it “ascended” fairly rapidly, it gave a warning about oxygen toxicity (OLF or oxygen limit fraction as used in the Suunto algorithm) and an ascent rate warning. On the right, at about 10 metres, a warning is given that the depth is still below the required level to complete the decompression.
All the green circular icons appearing around the middle of my dive, where the computer thought I was at 35 metres, indicate that the computer registered that I surfaced, but not for long enough to show on the dive profile. Weird!
My D6 remained angry for 48 hours after the dive at Doodles; by this time, we had finished our diving for the week. I’m not sure whether the problem with the pressure sensor is a permanent one (requiring repairs, a service or a new dive computer), or whether it was just dirty or stuck and will have resolved itself next time I dive with the instrument. I’ll be wearing a spare dive computer when I do, just in case.
On the second dive we did at Doodles during our trip to Ponta do Ouro, something happened that caused my dive profile to look like this (click on the image to embiggen):
Profile (from MacDive) of a dive at Doodles
Fortunately that something was not me falling down an 89 metre deep hole in the ocean floor whilst breathing off a 12 litre cylinder of air, 45 minutes into a dive. It was something going wrong with (we think) the pressure sensor of my Suunto D6 dive computer. I have had the computer for a few years, and apart from the compass appearing to have packed up, it has been a fantastic device.
The first inkling of trouble that I had was when the computer started beeping at me, and when I looked down to see what was up, it said we were at 89 metres. Sunlight was falling on me, so I thought this unlikely. I checked with Christo, and he didn’t think we were that deep either. Nor did his computer. Fortunately I had been diving with a group for a few days, and we were well within our decompression limits at a depth of 14-15 metres. Losing the computer three quarters of the way through a dive wasn’t the disaster it could have been.
I took this picture shortly after the beeping started. The display at the top of the screen shows that the computer is reading 76.7 metres. The maximum depth of 89.0 metres shows at the bottom left. The bottom right shows the oxygen partial pressure, at 1.9. This is greater than the 1.2 limit that I have set for myself inside the computer. The computer thinking that I had rapidly exceeded the maximum PPO2 is probably the initial cause of the beeping I heard.
Suunto D6 showing 76.7 metres’ depth
In the middle of the screen you can see a large number 8.0, which is the depth to which the computer wants me to ascend in order to do a decompression stop. Next to that number is an arrow below two horizontal lines, and the number 35. This is how long I should stop at 8 metres in order to fulfil the calculated decompression obligation.
The D6 thinks we have ascended to 47 metres now
After a few minutes (I was actually busy ending my dive with a 5 metre safety stop) the computer believed I had ascended to 47.3 metres. By that stage it wanted me to go to 11 metres for a 45 minute stop. When I surfaced after about 60 minutes of dive time, the computer stayed in dive mode, thinking that I was still at a depth of about 35 metres. It continued registering a slow, quite smooth ascent for another hour and a half, as seen in the dive profile above.
The computer was still very grumpy when it took itself out of dive mode in a mug of warm water in the bathroom of Planet Scuba, while we were eating a post-dive lunch. The ascent profile it registered did not fulfil the calculated decompression obligations, and it showed that I had violated my decompression ceiling (either by taking too long to ascend to start the stops, or by not spending enough time at the stop depth).
I have put myself briefly into deco a few times (usually during days of repetitive diving during dive trips, and once or twice in Cape Town with two relatively deep and long dives in a day), so the readouts from the D6 on this dive are not unfamiliar to me. I have never before, however, seen such large numbers or heard so much beeping! I have always corrected the situation by ascending a little way, which removed the decompression obligation and returned the display to what I am familiar with as a religiously recreational, no-decompression diver. In this case, the D6 was doing its own thing and nothing I did seemed to influence the depth reading it gave.
I found this to be an excellent opportunity to re-familiarise myself with the behaviour of the Suunto D6, and also to see what all the error messages look like on the dive profile when I downloaded the computer into the MacDive software I use for electronic dive logging. The story does not end here – if the computer did not think I was dead from DCI, it wasn’t going to let me dive any time soon – check back tomorrow (or the day after).
In this TED talk, self proclaimed “fish nerd” Pyle speaks about his work studying coral reef fish that live in the 100-200 metre depth range. This depth is too deep for scuba, and too shallow for submersibles, so Pyle pioneered the use of rebreathers (he was an early adopter, in 1994) to access this part of the ocean. This is a high risk pursuit, but the diversity and numbers of new species to be discovered here is stunning.
I first heard about Richard Pyle through Monty, who encouraged the readers of his Scuba Culture newsletter to check out an article Pyle wrote about an incident of decompression sickness when he was nineteen. The article is called Confessions of a Mortal Diver: Learning the Hard Way, and Monty is right – you should read it. Pyle actually mentions this incident right at the start of his talk. Watch below:
A news story in June resonated uncomfortably with me: a Nigerian sailor survived for two days in a pocket of air trapped beneath the tugboat he was in, which capsized in heavy seas. The tug was servicing an oil platform off the Nigerian coast.
I was immediately reminded of the Miroshga, an unseaworthy whale watching vessel that capsized in appalling conditions off Hout Bay in October 2012. The boat had its bilge pump installed UPSIDE DOWN, and was rated for over 40 passengers when it’s only five metres longer than our boat – which can take seven passengers (and when Seahorse is fully loaded, she feels full). Furthermore, the Miroshga hadn’t had a SAMSA inspection since fundamental changes were made to the vessel and its engines. The money-hungry decision to head out in a 25 knot south easterly wind and high seas was incredibly irresponsible.
Most people who go on seal cruises, whale watching or cage diving don’t spend half their lives on or near the sea, and simply don’t have the tools to assess whether conditions are safe and whether the boat is seaworthy. The passengers trusted the charter operator and SAMSA, and were badly let down. One man drowned, and three women were trapped under the boat in pockets of air for several hours, their limbs dangling in the freezing water, until rescue divers brought them out. I cannot imagine how traumatic the experience was for them. The rest of the passengers were rescued by a boat full of poachers, and by some incredible NSRI volunteers. It was a shameful day for the boat charter operators, and for those responsible for legislating and enacting maritime safety provisions in South Africa.
I digress. What happened in Nigeria? Out of the twelve crew on board the tugboat, ten bodies were recovered, one was lost, and the twelfth crewmember, Harrison Okene, was discovered alive, under the boat in 30 metres of water, surviving by breathing from an air pocket. Upon being rescued by divers sent to retrieve the crew’s bodies (can you imagine their shock at being greeted by a living person when they were expecting only corpses?), Okene had to undergo sixty hours of decompression in order to avoid being bent. He’d been breathing air at four atmospheres for two and a half days!
How large does the bubble have to be so that a person in it can have indefinite supply of breathable air?
The reason it’s even possible to have an “indefinite” supply of air is that if the bubble is large enough, oxygen will diffuse out of the surrounding water back into the bubble, and carbon dioxide won’t build up to fatal concentrations. You can read through the discussion if you want to (fun to see physicists arguing, nice if you like formulas!) or there’s a news article here about the theoretical bubble size that would be required for survival. Turns out the actual air bubble was close to the size calculated by the physicists that would allow survival for at least the time that Okene was submerged. Lucky, lucky man!
Update: Here’s the helmet cam video from one of the rescue divers who brought Mr Okene to the surface. The text at the beginning is wonky – persist. Note the South African accents! The diver’s voice is squeaky – I think because he’s breathing a gas mix with helium in it. It gets good at about 5:30 but it’s extremely interesting to watch in its entirety to see what sort of conditions these divers work in, and how the surface support talks them through their tasks and keeps them calm.
The four episodes of this History Channel series cover waves, tides and currents, predators, and pressure – all powerful features of the ocean that can be sensationalised (some more easily than others) and presented for shock value and as imminent threats to human life. Full advantage is taken of this fact.
This very American offering doesn’t boast the measured, mellifluous tones of Benedict Cumberbatch or Steve Toussaint as narrator, but the line-up of (mostly in-studio) guest narrators is quite impressive. Bruce Parker (The Power of the Sea), Susan Casey (The Devil’s Teeth and The Wave), David Gallo (scientist presenter of the TED Talk I mentioned here), Scott Cassell (student of the Humboldt squid), Richard Ellis (writer of a number of ocean history, art and sciencebooks), and Neil Hammerschlag (shark scientist) were familiar to me, as was big wave surfer Ken Bradshaw, from this article. The strange, uncomfortable way in which the studio narrators were filmed, with silent close ups interspersed with talking, was very annoying and must have been incredibly embarrassing to shoot. Or perhaps the cameraman took the footage when the narrators didn’t realise they were being filmed.
Unlike BBC documentaries, which tend to rely purely on incredible photography and fluent narrative to convey information, the History Channel favours a CGI-heavy approach that we encountered in Treasure Quest,Deep Sea Salvage, and also in the National Geographic SharkMen series.For the subject matter of this series – particularly the sections on waves, tides and currents – it was very appropriate and informative. The first episode, devoted to tsunamis, rogue waves and “monster waves”, made good use of CGI to illustrate the concepts as they were explained. The series was produced shortly before the Japanese tsunami of 2011 (there is a hastily tacked on “thoughts and prayers” disclaimer) and features interviews with a survivor of a tsunami in Samoa. I am fascinated by rogue waves – the whole episode could have been devoted to them but they don’t make for good television – we only have indirect evidence of their existence. Also, I could have done with more footage of giant ships battling storms, but that’s what youtube is for…
The least interesting and most irritating episode was the one devoted to the ocean’s top predators, which suggested that orcas are a serious threat to humans. As evidence, the cases of captive killer whales drowning and injuring their trainers at marine theme parks were cited. No mention was made of the psychosis that these whales suffer from as a result of confinement in a small, barren, completely unnatural environment. An incident in which orcas inexplicably rammed and sank a yacht in the Pacific Ocean is also described and re-enacted. Whether the orcas did what they did because they wanted to kill the people on board is highly debatable. There is also a half-hearted attempt to paint whales as potentially vicious killers, recounting incidents when sperm whales rammed whaling boats in the 19th century. More power to the sperm whales, I say.
The other dangerous predators were (predictably) white sharks, Humboldt squid, saltwater crocodiles and Australian box jellyfish. There was a small environmental message at the end of this episode, mentioning that squid will probably end up the top predators in our oceans if current trends – fishing out large predatory fish and global warming in particular – continue.
The third episode, on the immense pressures that objects in the deep ocean are subjected to, was very interesting to Tony and me as divers. A confusing interview with a diver whose brother got DCS on a wreck dive leaves (I suspect) much out. Were they even qualified divers? Why was he surprised that his brother felt unwell and confused as to the cause after he popped to the surface from 30 metres after a 30 minute dive?
The bulk of the third episode, however, recounts a 1981 experiment called Atlantis III in which three volunteers were taken in a saturation system to a simulated depth of 686 metres while breathing Trimix 10 (70% helium, 20% nitrogen and 10% oxygen). It took 31 days for them to decompress. The chief of the experiment, Peter Bennett, was the founder and former CEO of DAN. There’s a more information about the project here – worth a read (download the pdf slowly), and a briefer account here.
The series concludes with an episode on tides and currents, including rip currents. The massive tidal range of Morecambe Bay in the United Kingdom, is discussed at length. At low tide, up to 300 square kilometres of mudflats is exposed, and flooded again when the tide comes in. The guides who escort people out onto the mudflats when the tide is out seem like charming individuals – it is recommended not to wander around at low tide without local guidance. In 2004, the rising tide trapped and drowned 23 Chinese immigrants who were working the cockle beds – with such a large expanse of land to cover, the rising tide comes in at great speed. There is also a harrowing re-enactment of a father and his two sons getting washed out to sea in a rip current in Kauai that should make you think twice about swimming at beaches with warning signs on them.
You can get the DVDs here if you’re in South Africa. Foreigners, go here or here.
The wreck of the Andrea Doria, a luxury Italian cruise ship that sank in the north Atlantic ocean in 1956, is to some divers a sort of Mount Everest. It lies in about 70 metres of seawater, 160 kilometres from land. It has claimed ten lives to date and been the subject of several books and essays. Deep Descentdeals specifically with this wreck. Shadow Divers and The Last Divedescribe dives on the wreck, as well as featuring several of the regular charter captains and divers who pioneered diving on the Doria.
An Esquire article from 2000, written by Bucky McMahon (author of this article on Reunion’s shark problem), describes diving on the wreck, and attempts (as do they all) to pin down the allure of this particular piece of ocean debris. The article was written after a thirteen month period (late 1998- late 1999) during which five divers from the same charter boat (the Seeker) died on the wreck. It is written in a masculine, aggressive style that may be characteristic of McMahon’s writing, but is certainly characteristic of the sort of behaviour that seems to play (or have played) out on the Andrea Doria since people started diving her.
But how does it feel? What’s it like to know you are in a story that you will either retell a hundred times or never tell? You decide to drop down into the black hole. No, you don’t decide; you just do it. Why? You just do. A little ways, to explore the wreck and your courage, what you came down here to do. What is it like? Nothing under your fins now for eighty feet but the mass and complexity of the machine on all sides–what was once luminous and magical changed to dreary chaos. Drifting down past the cables that killed John Ornsby, rusty steel lianas where a wall has collapsed. Dropping too fast now, you pump air into your b.c., kick up and bash your tanks into a pipe, swing one arm and hit a cable, rust particles raining down. You’ve never felt your attention so assaulted: It is everything at once, from all directions, and from inside, too. You grab the cable and hang, catching your breath–bubble and hiss, bubble and hiss. Your light, a beam of dancing motes, plays down a battered passageway, where metal steps on the left-hand wall lead to a vertical landing, then disappear behind a low, sponge-encrusted wall that was once a ceiling. That’s the way inside the Doria.
Wired.com published an article in their Danger Room section, all about defence, concerning proposed DARPA research on biometric monitoring of navy divers. DARPA, the United States Defense Advanced Research Projects Agency, is the organisation that commissions advanced (and sometimes wildly unrealistic… until it’s realised) research for the US Department of Defense.
One of their latest research proposals is to come up with some kind of device that could monitor a diver’s vital signs while he’s in the water. One of the vital signs that the device should be able to read is the presence of nitric oxide, which works to prevent the bends (decompression sickness: the presence of excessive nitrogen in the blood after breathing compressed air at depth). Nitric oxide would then be added to the diver’s body if the levels of this gas fell too low. There’s a lot more to it…
(As an aside, it would be wonderful if modern dive computers could do this, but they can’t.)
The brief for the required research reads like an excerpt from the script of a James Bond movie. I actually laughed out loud reading the article, but that’s the reason I’m not doing cutting edge research: lack of imagination. It’ll seem ridiculous until someone actually invents it, and you can be sure that it’ll be used in military applications before us civilians get our grubby paws on it.
The History Channel series Deep Sea Salvage ran for one season of six episodes in 2009. The series follows the activities of salvage teams employed by Bisso Marine, a family owned salvage company that has been operating along America’s Gulf Coast and (more recently) beyond, for over 100 years.
The first few episodes involve the land and surface-based salvage of some partially sunken vessels in the Mississippi River and surrounds, and a number of barges pushed far inland by a storm surge. I can’t prove it, but I strongly suspect that much of the mayhem that the salvage teams are required to fix occurred as a result of Hurricane Katrina.
Later episodes deal with salvage divers who venture (alone) 100 metres below the surface of the Gulf of Mexico to shackle giant chains to a wayward oil rig leg, or into murky, fast flowing river waters to determine whether a wrecked barge still contains toxic oil in addition to what’s already spilled out and polluted the river. The diving shown isn’t saturation diving.
The show is edited (I think) to make the action seem quite rapid and to take place over short periods, but in some cases there must be a lot of waiting – for weather, gear, support – involved. Tony and I would have liked to see more detail about the dive planning, the gas mixtures used (for the deeper ones helium seems to be involved, because the divers’ voices over the radio were hilariously squeaky) and the logistics of dealing with potential decompression sickness while on a crane barge out at sea. The show isn’t really about that, though; it’s concerned with the work the divers do underwater, but not so much how they get there and back. We were gripped by the dive footage, despite this.
Everything is enormous. The barges and oil rigs are colossal. The winches, cranes, chains, blocks and pulleys, ropes and other equipment such as inflatable bags (large enough to rest a barge on top of a few of them) are all giant-sized. Working with such massive gear requires planning; one can’t quickly pop back to the office to pick up a winch one has left behind, or quickly pick up a chain and move it out of the way of an earth moving machine. Out at sea the constraints are even more severe. Most of the jobs covered in the series were so mind-boggling to me that I would have ordered the vessels scrapped – one can’t even imagine that it’s possible to remedy some of the situations shown. And yet somehow it is, and the Bisso teams do.
Something else that makes this a fine series to watch is that one of the slightly senior salvage team members is called “Lunchbox”. You read that correctly.
