The divers who worked refurbishing NYC’s aqueducts spent a month at a time living and working from an underwater habitat with a helium atmosphere and all the modern conveniences including a basketball hoop. I gather welding was just one of their jobs.
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When I took SCUBA diving classes they showed a bit about the training one could continue taking to get advanced certification for activities up to and including underwater welding. I remember learning the hourly pay was crazy high, but of course that’s because A) very few people can do it and B) it’s also crazy dangerous.
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There are some subtleties here in that as a whale dives the air in its lungs will inevitably become compressed, but if its alveoli collapse then gas exchange with the compressed air will shut down. I assume they have some adaptations to pull off this trick without damaging their lungs.
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not the same mechanism involved here. yes, the air in the lungs compresses along with the lungs themselves, but that breath was taken at surface air pressure. a diver breathing compressed gasses from a tank at depth has a whole different set of physics going on that make ot something to be very cautious about, especially at depths where pressures exceed one atmo of pressure (10 meters/33 feet down).
human free divers can dive down hundreds of feet on a single breath, have that air compress as their bodies are under pressure down deep. thing is, as the diver surfaces and the air expands it will not exceed the volume in the lungs of the original breath. breathing from a compressed gas cylinder at, say, 20 meters and surfacing rapidly (more than 1 foot/ second) that air will expand to greater volume and can burst the lungs (air embolism). nasty.
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That helps. But free-diving humans have developed decompression illness. Rare, but that’s believed to be due to limitations of how deep / long humans can free dive compared to e.g. walruses, whales, etc. If humans could do half-hour dives to 200 feet with the physiology we have, there’s little doubt we’d see a lot more Taravana syndrome.
Two episodes of Taravana syndrome in a breath‐hold diver with hyperhomocysteinemia - PMC.
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decomp sickness =/= embolism (as a diver you already knew that). free divers have gone well below 200 feet as this attached listicle notes, the record free dive (breath hold dive) is 214 meters (that’s just over 700 feet!).
again though, just like marine mammals, free divers take that breath at surface air pressure. that volume of air cannot expand in volume more than when it was inhaled in the first place. that fact of physics is the same for whales, dolphins, seal, walrus or any other marine mammal that dives deeper than 10 meters.
this of course does not address Taravana in human free divers. it is still very dangerous, but not thoracic explosion dangerous!
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I know a couple of salvage divers, and that’s hard enough. Plus a couple of inspection divers with seriously icky stories. No thanks on any of these occupations, but I’m thankful there are people willing (or crazy enough) to do them.
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