5 ms·

Thats quite deep for the region. TIL Baltic Sea is 55m deep on average, but 80m deep in the region where cable was cut. That also means that 2nd easiest to acq

by agilob 2y ago

Thats quite deep for the region. TIL Baltic Sea is 55m deep on average, but 80m deep in the region where cable was cut. That also means that 2nd easiest to acquire PADI qualification is enough to dive there by yourself.

echoangle 2y ago
> That also means that 2nd easiest to acquire PADI qualification is enough to dive there by yourself. How? Open water diver is 18m, advanced Open water diver is 30m. With „deep diver“ specialty, you’re at 40m. I think you need to become an instructor to go deeper, that’s not the 2nd easiest qualification at all.
- rich_sasha 2y ago
  I think PADI doesn't even go that far, it is predominantly a leisure diving organization. Their technical diving courses seem to end at 50m. Not really related to instructor courses either, a regular instructor typically has no need to go beyond 30m. Diving to 80m is a serious endeavor on this scale.
  - weebull 2y ago
    80m is moderately serious. I've personally done 75m in the Atlantic and I wouldn't say I'm superhuman or anything (or military). It requires helium mixes and personally I'd only want to do it with a rebreather, not normal "blowing-bubbles" type SCUBA gear (too wasteful on the breathing gas). 20-30 minutes at the bottom will mean around 90-120 minutes decompressing. You don't want to be doing anything taking too long, or being too laborious. Could be done from a fishing boat without any problem.
    - rich_sasha 2y ago
      Yes, it's very doable given the right training. But it's not really an extension of what a typical "PADI diver" might do, is what I meant. Having had equipment failures no deeper than 30m, I decided any dives that require decompression are not for me. I'll leave deep dives and sabotage to others :)
    - wkat4242 2y ago
      You know, I never dove but I always wonder, why do deep divers not breathe a nitrogen-free atmosphere before they dive to flush out the nitrogen? I understand astronauts do this too (they breathe pure oxygen but at a lower pressure so it's not dangerous). And because this a sudden pressure drop won't give them the bends. It would seem simple, being able to deep dive then without decompressing. I'm sure there's a good reason it's not being done, I just wonder what.
      - rich_sasha 2y ago
        I think what you breathe pre-dive is almost irrelevant. The real kicker is what you breathe during the dive, and that's always going to be gas under pressure. The levels of gas in your blood go up very quickly. Recreational divers can only afford ~10-20 minutes at 30m depths before they need to decompress. And that doesn't even count as "deep". You can't breathe pure oxygen under water, as it becomes very toxic very quickly as pressure goes up. So you have to dilute it with something. Nitrogen is easy to get hold of (actually you just compress atmospheric air). I'm also not sure cutting nitrogen out helps much with decompression sickness, you get it with other gases too - maybe more slowly, I'm not sure. You can, and do, replace nitrogen with other gases, mostly helium (and in rare circumstances, hydrogen), but for other reasons. Nitrogen too becomes toxic under pressure, around the 30-40m mark, with symptoms similar to drunkenness - not good under water. Funnily enough, helium does the same deeper down, except the symptoms there are the opposite - nervousness, tension etc. So to some extent perhaps these two balance out. Hydrogen has very low toxicity, but for some reason people feel queasy about mixing pure hydrogen and oxygen. Crucially, too, a lot of deep diving is commercial in nature, and cost-sensitive. Anything that isn't just compressed and bottled air is getting very expensive very quickly. It all gets incredibly complicated. Deep enough, you need to breathe gas that contains so little oxygen that you would suffocate on it at surface pressure. At pressure, it's fine - the partial pressure of oxygen is sufficient, and having less of it makes it less toxic. But you have to be careful to only use this gas deep enough, else you'll run out of oxygen. Or at other times, when decompressing, you might use an oxygen-rich mix, which while more toxic, helps you purge some of the other gases from your bloodstream, cutting decompression times. It's a fascinating topic to read about from the comfort of my sofa.
      - 2y ago
- belorn 2y ago
  > How? Open water diver is 18m, advanced Open water diver is 30m. With „deep diver“ specialty, you’re at 40m. Correct. Those are the limits of those certifications. > I think you need to become an instructor to go deeper, that’s not the 2nd easiest qualification at all. In order to go down to deeper depths and returning you generally need a technical or professional certification. Anyone can go to any depth, as long they don't expect a reasonable chance to get back to the surface alive. PADI open circuit technical course go down to 50 but there are other agencies for technical diving with a bit better reputation, and those generally max out at 100. Most people who are trained for 80+ depth usually do so on a rebreather. Padi do have a 100m course for that. However with rebreathers, students mostly look towards specific instructors and not agencies. What agency a instructor uses is generally much less important than that you trust the instructor.
jakedata 2y ago
Anybody can dive there. Surviving the trip back up is what most of the classes are for.
hnarn 2y ago
There is no reason to dive, large freight ships can have anchors with chains several hundred meters long.

by agilob 2y ago

echoangle 2y ago

> That also means that 2nd easiest to acquire PADI qualification is enough to dive there by yourself. How? Open water diver is 18m, advanced Open water diver is 30m. With „deep diver“ specialty, you’re at 40m. I think you need to become an instructor to go deeper, that’s not the 2nd easiest qualification at all.

rich_sasha 2y ago
I think PADI doesn't even go that far, it is predominantly a leisure diving organization. Their technical diving courses seem to end at 50m. Not really related to instructor courses either, a regular instructor typically has no need to go beyond 30m. Diving to 80m is a serious endeavor on this scale.
- weebull 2y ago
  80m is moderately serious. I've personally done 75m in the Atlantic and I wouldn't say I'm superhuman or anything (or military). It requires helium mixes and personally I'd only want to do it with a rebreather, not normal "blowing-bubbles" type SCUBA gear (too wasteful on the breathing gas). 20-30 minutes at the bottom will mean around 90-120 minutes decompressing. You don't want to be doing anything taking too long, or being too laborious. Could be done from a fishing boat without any problem.
  - rich_sasha 2y ago
    Yes, it's very doable given the right training. But it's not really an extension of what a typical "PADI diver" might do, is what I meant. Having had equipment failures no deeper than 30m, I decided any dives that require decompression are not for me. I'll leave deep dives and sabotage to others :)
  - wkat4242 2y ago
    You know, I never dove but I always wonder, why do deep divers not breathe a nitrogen-free atmosphere before they dive to flush out the nitrogen? I understand astronauts do this too (they breathe pure oxygen but at a lower pressure so it's not dangerous). And because this a sudden pressure drop won't give them the bends. It would seem simple, being able to deep dive then without decompressing. I'm sure there's a good reason it's not being done, I just wonder what.
    - rich_sasha 2y ago
      I think what you breathe pre-dive is almost irrelevant. The real kicker is what you breathe during the dive, and that's always going to be gas under pressure. The levels of gas in your blood go up very quickly. Recreational divers can only afford ~10-20 minutes at 30m depths before they need to decompress. And that doesn't even count as "deep". You can't breathe pure oxygen under water, as it becomes very toxic very quickly as pressure goes up. So you have to dilute it with something. Nitrogen is easy to get hold of (actually you just compress atmospheric air). I'm also not sure cutting nitrogen out helps much with decompression sickness, you get it with other gases too - maybe more slowly, I'm not sure. You can, and do, replace nitrogen with other gases, mostly helium (and in rare circumstances, hydrogen), but for other reasons. Nitrogen too becomes toxic under pressure, around the 30-40m mark, with symptoms similar to drunkenness - not good under water. Funnily enough, helium does the same deeper down, except the symptoms there are the opposite - nervousness, tension etc. So to some extent perhaps these two balance out. Hydrogen has very low toxicity, but for some reason people feel queasy about mixing pure hydrogen and oxygen. Crucially, too, a lot of deep diving is commercial in nature, and cost-sensitive. Anything that isn't just compressed and bottled air is getting very expensive very quickly. It all gets incredibly complicated. Deep enough, you need to breathe gas that contains so little oxygen that you would suffocate on it at surface pressure. At pressure, it's fine - the partial pressure of oxygen is sufficient, and having less of it makes it less toxic. But you have to be careful to only use this gas deep enough, else you'll run out of oxygen. Or at other times, when decompressing, you might use an oxygen-rich mix, which while more toxic, helps you purge some of the other gases from your bloodstream, cutting decompression times. It's a fascinating topic to read about from the comfort of my sofa.
    - 2y ago
belorn 2y ago
> How? Open water diver is 18m, advanced Open water diver is 30m. With „deep diver“ specialty, you’re at 40m. Correct. Those are the limits of those certifications. > I think you need to become an instructor to go deeper, that’s not the 2nd easiest qualification at all. In order to go down to deeper depths and returning you generally need a technical or professional certification. Anyone can go to any depth, as long they don't expect a reasonable chance to get back to the surface alive. PADI open circuit technical course go down to 50 but there are other agencies for technical diving with a bit better reputation, and those generally max out at 100. Most people who are trained for 80+ depth usually do so on a rebreather. Padi do have a 100m course for that. However with rebreathers, students mostly look towards specific instructors and not agencies. What agency a instructor uses is generally much less important than that you trust the instructor.

jakedata 2y ago

Anybody can dive there. Surviving the trip back up is what most of the classes are for.

hnarn 2y ago

There is no reason to dive, large freight ships can have anchors with chains several hundred meters long.