large air bubble on a deep dive

[Powertrip]

Water "transfers" pressure, so a diving bell or a hypothetical air pocket are at the same pressure as the water enclosing them, well not dive bells because they are isolated from the ambient pressure but that is a whole other explanation. It does nothing to your tissue saturation that the water was not already doing.

I appreciate the answer. Once I got the first actual response to the question it was ‘oh, duh’ I’ve done a lot of YouTube watching on saturation diving and salvage diving and knew those bells had to be pressurized to ambient pressure down there. And if id thought about it more I hopefully would’ve made the connection about air pockets

I threw myself for a loop comparing atmospheric dive suits to caves, completely overlooking that one is a closed environment and one isn’t

 

[Akimbo]

I haven't even taken my rec OW course, but my brain is always going on about what ifs.

I assume you mean 600-800' horizontally into a cave rather than a cave that is 600-800' deep. Breathing the air in a dry cavern would not change decompression compared to breathing air from your tanks. This thread may be help you understand decompression better:

Info - Decompression & Treatment Simplified

1: Introduction Everything should be made as simple as possible, but not simpler — Albert Einstein (paraphrased) I probably violated the "But Not Simpler" part, but I tried to include enough Hyperlinks to make amends. Clicking on them should allow any interested diver to "drill-down" as far...

scubaboard.com

 

[Wibble]

@Powertrip - do have a look at that film: Last Breath. Very interesting.

 

[Powertrip]

@Powertrip - do have a look at that film: Last Breath. Very interesting.

I will! I’m sure it’ll help with my questions

 

[rmssetc]

The concern about the computer is that the air pocket is pressurized beyond sea level. It's going from a pressurized water environment to a pressurized air environment.

Like I said, I never saw it happen, but didn't want to try it. I think the first time I heard it was from one of the computer manufacturers.

This is pure speculation on my part (but hey, that's 99.99% of all responses on SB, if you subtract out the vitriol and accident reports), but I wonder if the concern is with computers that have an immersion sensor (ie., automatically turn on when submerged in liquid), and if there's any chance that the computer will get "confused", such as thinking the dive has ended since it is no longer immersed, but it remains under high pressure. This would be the inverse of surfacing after diving at altitude -- in that case the computer recognizes that the dive is over, but that ambient surface pressure is less than sea level.

In this wacky scenario, the computer could think that the dive is over and that ambient pressure is at several ATM...in which case, resuming the dive (ie, leaving the air bubble and returning to the surface) would show a continuously ascending profile.

Of course, it's unlikely for the computer to be out of the water long enough for all the water at the immersion contacts to dry off, unless you're stuck in a cave in Thailand for days.


Anyway, this is a silly tangent in response to valid, well-intentioned questions from a soon-to-be diver.

@Powertrip , welcome to Scubaboard.

 

[Powertrip]

I assume you mean 600-800' horizontally into a cave rather than a cave that is 600-800' deep. Breathing the air in a dry cavern would not change decompression compared to breathing air from your tanks. This thread may be help you understand decompression better:

Info - Decompression & Treatment Simplified

1: Introduction Everything should be made as simple as possible, but not simpler — Albert Einstein (paraphrased) I probably violated the "But Not Simpler" part, but I tried to include enough Hyperlinks to make amends. Clicking on them should allow any interested diver to "drill-down" as far...

scubaboard.com

I did mean depth rather than how far in. Because the example made it clear I was talking about the idea of going from extreme pressure to surface pressure. Because I hadn’t followed the thought process through to the conclusion that in my example there was no measurable pressure difference

 

[Akimbo]

I did mean depth rather than how far in.

In that case, see this thread:

Info - What is Saturation Diving?

A lot of divers are not sure what Saturation diving is so I thought a quick summary might be useful. Saturation diving was developed by the US Navy's Captain George F. Bond (affectionately known as Papa Topside) in the 1960s. All divers know that the deeper we go and longer we stay, the longer...

scubaboard.com

My deepest lockout was a little shy of 950'/290M, supported divers to 1010'/308M, and built sat diving systems to operate below 1,640'/500M.

 

[Cthippo]

Actually, this raises an interesting question of locking into a submarine. Even at periscope depth that is still something like 60 feet below the surface to the hull where the escape trunk is. I'm not sure how fast they can pump out the trunk once closed, but it seems like something you would have to watch because you would be going from several atmospheres to one, which is ambient inside the boat. Do they have fine enough control over the pumping to account for deco?

 

[Guille G]

This is pure speculation on my part (but hey, that's 99.99% of all responses on SB, if you subtract out the vitriol and accident reports), but I wonder if the concern is with computers that have an immersion sensor (ie., automatically turn on when submerged in liquid), and if there's any chance that the computer will get "confused", such as thinking the dive has ended since it is no longer immersed, but it remains under high pressure. This would be the inverse of surfacing after diving at altitude -- in that case the computer recognizes that the dive is over, but that ambient surface pressure is less than sea level.

In this wacky scenario, the computer could think that the dive is over and that ambient pressure is at several ATM...in which case, resuming the dive (ie, leaving the air bubble and returning to the surface) would show a continuously ascending profile.

Of course, it's unlikely for the computer to be out of the water long enough for all the water at the immersion contacts to dry off, unless you're stuck in a cave in Thailand for days.


Anyway, this is a silly tangent in response to valid, well-intentioned questions from a soon-to-be diver.

This is just some further speculation on my part, but it seems that dive computers (at least the oceanics that I’ve used) only use the wet sensor to turn on, since they start to“end” the dive when you are within a meter or so of the surface and the computer is still wet. If they detect that pressure increases again before 10 mins, they resume the dive. If not, they totally end it and start counting the surface interval.

So, speculating based on that behavior, I’d bet that emerging in a pressurized pocket would still be interpreted as being at depth and diving even with a dry contact.

Of course, this is not in the manual - but it’s the behavior that makes sense based on how they operate.

 

[Akimbo]

Actually, this raises an interesting question of locking into a submarine.

All the world's navies, especially the submarine forces, understand decompression. Not to worry.