https://ibb.co/zbLSRzH
I’ve attached an image here, to further illustrate the scenario. Imagine that the wreck is at the bottom of the Marianas trench, 10km underwater.
Would jumping into the water kill you from the pressure? Or would it only kill you if you swam to where there is no cover on the right side of the wreckage?
In: Physics
No, you can’t put something above you to protect you from water pressure. It pushes in on you from all sides, including pushing upwards against the air bubble you’re in. Which means the air bubble must be pushing back just as hard. Which means the air bubble is already at that 10km depth pressure. Whether you’re crushed by the water or the air, it’s already happened. Sorry, you’re already dead.
The air itself in the pocket would be pressurized. If the pocket had a lower pressure than the surrounding water, the water would rush in from the bottom and compress the air pocket until an equilibrium was reached.
So no, jumping into the water wouldn’t change the pressure you feel in any way, nor would swimming outside of the wreck. The water is all around you, so just a rigid “lid” somewhere above you wouldn’t change the pressure you feel at all.
Neither of your options is correct.
Remember that the water isn’t flowing into the air pocket because the air is pushing back just as hard as the water. All the water at that depth is under the same pressure, as otherwise there would be a flow from the higher pressure area to the lower.
So the air the person is in must be the same pressure as the water at that depth. Stepping into the water would have zero change in pressure on their body.
In your situation there is nothing keeping out the pressure in the first place. The air bubble pressure would be less than the pressure of the water, so the water would enter your bubble, compressing the air, until the pressures were equal. You’d never get a chance to consider your question you’d just be crushed.
If the pocket is open to the water, the pressure inside must by definition be equal to the pressure outside. If the pressure were *not* equal, then either water pressure would force water in, or air pressure would force water out – until the pressure is equal. If the pressure is enough to kill you in the water, it’s enough to kill you in the air pocket.
When people talk about air pockets in sunken ships, they are either talking about ships that sank in shallow areas where the pressure is not lethal; or, pockets that are entirely sealed off and the structure itself resists the pressure enough for them to survive. In a submarine, the air pressure inside is far less than the water pressure outside. That works because although the water is trying to crush the vessel with all that pressure, the hull is strong enough to withstand that pressure and prevent the water pressure from winning ([unless it isn’t and it doesn’t](https://en.wikipedia.org/wiki/Titan_submersible_implosion)).
On many naval ships, various bulkheads are designed to close off sections of the ship if it starts taking on water, hopefully to keep the ship from sinking. If the ship *does* sink, those closed off areas may be sealed well enough to hold off the pressure. This may end up being a *worse* fate, depending on how you look at it, because [survivors often cannot be rescued](https://www.seattletimes.com/nation-world/16-days-to-die-at-pearl-harbor-families-werent-told-about-sailors-trapped-inside-sunken-battleship/). As you might imagine, you can’t just cut a hole to let them out, because that would the water and the water *pressure* in, killing them quickly, if not instantly. Of course, even if you could get them out of there, you couldn’t get them *in* to your own rescue vessel for the same reason – opening your vessel would mean allowing in the pressure.
[This guy](https://amp.theguardian.com/lifeandstyle/2023/sep/26/i-survived-three-days-in-a-capsized-boat-on-the-ocean-floor-praying-in-my-air-bubble) got trapped for 3 days in a shipwreck. He still had to spend multiple days in a decompression chamber afterwards.
As the ship was sinking, the air in the bubble with you would have been compressed. As you get deeper, the water level in the air pocket would get smaller. It’s the same amount of air, but under more pressure, so occupying a smaller space.
In the air bubble, you’re practically under the same pressure as the water at your feet.
It depends on the depth. If this happened in shallow water, no. There’s actually a few recorded incidents of people surviving for days in those air pockets before being rescued. However, this really only works in shallow waters, down to 300 meters (equivalent to 30 atmospheres), and even that is likely to fuck you up. See, if there is an air pocket, that means that the air in that pocket is under pressure. The water is pushing against the pocket, and so the pressure must increase to match the pressure of the water. Now, while we’re designed to survive in one atmosphere, we can sustain considerably more if the situation demands it, so long as the pressure is equal inside and outside our bodies. However, at 10 kilometers depth, you are dead. See, water pressure increases by one atmosphere every 10 meters. That means at a depth of 10 kilometers, you’d be experiencing 1000 atmospheres of pressure. That’d kill you outright, no way for you to survive that.
There is that one guy who was found in a ship wreck. With the boat upside down and he was in a big air pocket for weeks. And I think they had to put him in a air bell on the way up. So his body would get used to normal air pressure. Because of him being at that depth for so long. I just can not remember what the event was called. Like the name of the ship wreck.
Yes you would die instantly.
BUT the only way you would be able to “jump” into the water is if there was metal or something preventing water from getting in. To get out of that sealed in air pocket, you would need to somehow punch a hole into the metal which would almost instantly let water in which will implode you.
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