large air bubble on a deep dive

[Jack Gomez]

I haven't even taken my rec OW course, but my brain is always going on about what ifs. So here we go... You're on a deep dive, say 600-800 feet. in a cave and you walk out into a dry cavern... what kind of havoc is this going to play on decompression? or say a longer dive at 200-400 feet and then you pop up into air in a cavern... Your body clearly isn't under the same pressure as when in the water. My mind says you'd be in pretty rough shape, but on youtube I'm seeing videos of guys cave diving and coming up into air pockets and chilling for awhile. Same for people using diving bells as deco stops. is there a lot I just haven't learned yet/missed?

Lots of comments about the depth, but I understand that you are providing a hypothetical scenario. Regarding a different aspect of your question, there are instances where a diver can enter an air pocket and breath the air in the pocket. I have done this in Palau. The depth was less than 50 feet and the limestone caverns have airflow to the surface as the limestone is permeable.

 

[wetb4igetinthewater]

Please don't let the snarky responses keep you from asking questions. Chances are pretty good that if you had the question, lots of other people did too. The people who are dishing on you for not intuitively knowing the answer to this are doing so to make themselves feel superior. For those folks, kindly keep the sarcasm and look-down-your-nose-ishness out of the diving physiology and medicine forum. As a reminder, this is a learning zone.

To the OP,

Always listen to this person. There are multiple reasons why someone may ask a "bad" question (it wasn't bad in my opinion at all, but one that invited discussion), but the person should be dealt with respectfully and have their question answered with sufficient explanation. In addition, any discussion that involves a response from DDM is a good one.

View attachment 721264

This sadly happens all too often on social media. Few of the snarky comments here would dare say this in person.

 

[Powertrip]

Lots of comments about the depth, but I understand that you are providing a hypothetical scenario. Regarding a different aspect of your question, there are instances where a diver can enter an air pocket and breath the air in the pocket. I have done this in Palau. The depth was less than 50 feet and the limestone caverns have airflow to the surface as the limestone is permeable.

See this was why I’d initially overlooked the pressure being equal. Thinking that sometimes there’s ways for fresh air to get in, what keeps the pressure high enough to keep the water out and equal to the water depth

To everyone who has given me useful guidance, even when why I was asking what I was asking wasn’t clear, thank you. It was greatly appreciated

 

[dlofting]

I read the OP and have been thinking about it all day. I can't figure out how geology and physics could result in an air pocket in a natural cave at 600 feet of water. I hesitated to post because my question is a bit off topic, but I can't get it out of my head.....what, if anything, am I missing here?

 

[Wibble]

I read the OP and have been thinking about it all day. I can't figure out how geology and physics could result in an air pocket in a natural cave at 600 feet of water. I hesitated to post because my question is a bit off topic, but I can't get it out of my head.....what, if anything, am I missing here?

V. good point.

It’s unlikely to be "fresh" air. Could well be gas, almost certainly foul.

 

[Powertrip]

V. good point.

It’s unlikely to be "fresh" air. Could well be gas, almost certainly foul.

If my creativity gets me to that point, it'll be a fun plot device!

 

[rx7diver]

I haven't even taken my rec OW course, but my brain is always going on about what ifs. So here we go... You're on a deep dive, say 600-800 feet. in a cave and you walk out into a dry cavern... what kind of havoc is this going to play on decompression? or say a longer dive at 200-400 feet and then you pop up into air in a cavern... Your body clearly isn't under the same pressure as when in the water. My mind says you'd be in pretty rough shape, but on youtube I'm seeing videos of guys cave diving and coming up into air pockets and chilling for awhile. Same for people using diving bells as deco stops. is there a lot I just haven't learned yet/missed?

Sort of related: Google "caisson disease." It was a mystery until relatively recently.

rx7diver

 

[Akimbo]

It is sort of academic if the air pocket at 800' is fresh or not since the PPO2 would be 5.3 ATA.

 

[MikeinAA]

It is sort of academic if the air pocket at 800' is fresh or not since the PPO2 would be 5.3 ATA.

at 800 feet an “air” pocket if it existed would probably be methane and co2 from something decomposing or sulphur dioxide plus co2 from under water volcanic activity. Either way don’t breathe it.

 

[Akimbo]

at 800 feet an “air” pocket if it existed would probably be methane and co2 from something decomposing or sulphur dioxide plus co2 from under water volcanic activity. Either way don’t breathe it.

True but the premise was an air pocket. We haven't even mentioned HPNS, compression arthralgia, or hypothermia yet.