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First of all, I tried to look if this wasn't answered before. Found this and this but neither is exactly what I need.

Some Context

There's this race of humanoid fish people. They live in cities built on the ocean floor of the planets they inhabit.

For some plot reason, they decided to come to Earth. In order to remain hidden, they built their advanced post in a very deep part of the ocean floor.

Their "city" is but a collection of domes with breathable air inside. But they're not made of glass - they're "force fields" that repel the water. This means that if you're inside, you can literally get out and swim (since there's nothing solid between the air and the water). Which brings us to my question.

The Question

Picture an amount of pressure that would be way more than what is necessary to kill a human being (I have no idea what this number is, so I'll just guess 1000 meters down).

Given this ridiculous amount of water pressure, what would such a death look like to a bystander?

For this, just imagine you're inside the dome and someone else gets thrown in the water in front of you, exposed to 1000 meters (or more) of water pressure. I want to know what happens to this guy.

Does he get crushed? Bleeds from all orifices? Explodes? If you could also tell me how bad it gets with even greater depths, that would be super. If 1000 meters is too low, feel free to increase it up as much as you can, as long as it's still Earth parameters.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch ♦
    Dec 18, 2018 at 20:25
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    $\begingroup$ if the force field repels water, what happens when something like your hand which is mostly water touches it or tries to go through it? would it rebel your hand back inside before you could touch it? or would it pull you through? tear your arm off? pull the water out of your body? $\endgroup$
    – Zack
    Dec 19, 2018 at 20:41
  • $\begingroup$ maybe I'm being to anal or literal. its just what I thought of when I read your question. $\endgroup$
    – Zack
    Dec 19, 2018 at 20:42
  • $\begingroup$ @Zack I'll comment on your question in the chat L.Dutch created, since he's called attention to it. I'm still kind of new here so if these comments need to be moved to the chat as well, I don't know how to do it. $\endgroup$
    – Magus
    Dec 20, 2018 at 13:12

8 Answers 8

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You would die quite instantly.

L.Dutch's answer is accurate if you do the shift on a reasonably short timescale. But if you do it really fast, which I'm getting the impression is your goal, the story is a bit worse.

It is true that most of the body is solid or liquid, and thus basically non-compressible. Only the air volumes will be squished. However, when you do this quickly you run into fun problems with how quickly the air can be scrunched.

1000m down means you have 100atm of pressure on you. That's 1400 pounds per square inch of your body. For a comparison, you're looking at the pressure a woman puts on stiletto heels when she strikes the floor. Your entire body will be subjected to this pressure and transfer it to the air volumes.

But it can't do this instantly. It takes time. While it's happening, that pressure gradient is still an issue. Only after its done is the body pressurized enough to equalize that force.

So during those first few moments, it will literally be as if a woman was driving stilletto heels into your windpipe in every direction. Tissues would accelerate inward at a speed limited only by the ability to accelerate the water into the space as the tissue is shoved towards the air pockets. I do believe the only limit to speed here is the speed of sound in water, which is quite high.

Now... have you heard of water hammer? Water really doesn't like to be slowed down. So once the air pockets are gone, the water pressing in on you will keep going.

Remember that water cutter from my comments? This is not going to go well. But it will be swift enough to be painless.

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    $\begingroup$ A 1cm deep "plug" of water will be moving at 140 m/s (500 km/h) by the time it travels 1 cm in a 100 atm gradient. Youch. $\endgroup$
    – Yakk
    Dec 17, 2018 at 21:09
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    $\begingroup$ Some numbers to add to this answer: Human lung volume is about 6 litres. Filling that in at 100 atmospheres of pressure means about 6 kilojoules of energy are released. That's about as much as the kinetic energy of a rifle bullet. $\endgroup$
    – Thomas
    Dec 18, 2018 at 23:49
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Pressure will act on the fluids in the body, thus gases and liquids.

Liquids

Well, liquids are practically non compressible, meaning that even applying large pressures they won't change in volume in an appreciable manner. So blood vessel, eyes, brain, etc. will not be severely affected.

Gases

Gases are contained mainly in the lungs, intestine and stomach. They will shrink to match the outer pressure (this is why when one dives after a certain depth the buoyancy is negative). The lungs are pretty spongy so the shrinking per se should not be traumatic, however it will practically nullify the exchange area, leading to suffocation.

The gas contained in the intestine and the stomach will be squeezed, too, leading to the abdomen being flattened out. Since the lungs are also shrinking I suspect the bowels would move upwards pushing on the diaphragm. That's probably not as quickly lethal as the suffocation, but I am pretty sure is really painful.

The eardrum will surely be perforated by the high pressure differential between the outside environment and the inner ear. In itself this is not lethal, but again it is painful.

Summary

Summarizing, the poor guy would die of suffocation with two perforated eardrums and flattened out bowels. Which is not a particularly spectacular way of dying, but it is rather painful.

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You would find it near impossible to push someone out, let alone trow him out. To "push" 80 kg man out against 10 MPa pressure would need around 800 kJ of work and a push of 50-100 tonnes if you go head/legs first.

Maybe your dome can make pockets to eject or you have special building with "airlocks" to trow him in and fill it full with water.

How happy will our lucky winner be? There is 1000 tonnes of water over every square meter and water loves to hug things inside and around it and give all that love equally to every centimeter of the surface. With surface area of 1.7-1.9 square meters you will feel 1700-1900 tonnes of love.

Such a warm hug will compress all gases, partially heating them up and then squeeze out of you with good measure of bodily fluids, while crushing your sternum, cracking your skull and many other bones, compacting your body in to more dense human-like brick.

Show of compacting human with visuals of bubbles and cloud of bodily fluids and sounds of cracking and snapping. Near instant death, if you flood chamber fast.

Speed of water flow would be 140 meters per second. If you want you could use that as water jet cutters. They won't instantly cut bones, but enough to cut and tear apart flesh like nothing.

May as well add magical swap. If you get swapped with same volume of water. Water close to instantly squeezes you with same force as stated above. All your internal cavities with air inside will be crushed to just a fraction of their original volume. At the same time few liters of water will force their way into you. Soon compressed air will bubble out of you and water around dyed slight pink with blood from torn tissues.

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  • $\begingroup$ I don't think this is accurate, water would be rushing into you, nothing would be getting out $\endgroup$
    – Andrey
    Dec 17, 2018 at 19:16
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    $\begingroup$ Result strongly depends on how you flood the chamber. I would use low volume chamber with big diameter holes to flood it. At such depth water will ram in to you at 500 km/h from one or multiple sides. But yes, some water will get inside. $\endgroup$
    – Artemijs Danilovs
    Dec 17, 2018 at 19:27
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    $\begingroup$ OP seems to mostly be asking what would happen if someone is magically teleported in. We are assuming no impact trauma. $\endgroup$
    – Andrey
    Dec 17, 2018 at 19:29
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As a starting point here is a video of an egg at 6,000 bar
video
1 bar is 10 meters, so we are 60,000 meters underwater.

So if you look at the egg from the outside there is nothing wrong with it. The shell withstands the pressure just fine. Once the egg is cracked open all the proteins have congealed, and the egg is "cooked" but from the outside it is just fine.

The same thing would happen to a human. While internally they would be crushed, with water rushing into every orifice, breaking barriers like eardrums and filling the person, from the outside they would look not very different.

Unconsciousness would be instant as the brain stops functioning the moment cranial pressure hits a high mark. The water would most likely flow around the eyes past the optic nerve pushing them in long enough to stabilize the pressure.

Then the probably discolored human would just sink. There would be no gasses left to keep them buoyant. Chemically they would be ruined, but physically they would not look very different.

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  • $\begingroup$ Would it be the same for a human, given our lack of relatively hard shells? $\endgroup$
    – JMac
    Dec 18, 2018 at 15:53
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    $\begingroup$ @JMac It's not the fact that it's a hard shell keeping it together, it's the fact that the internals of an egg are (nearly) incompressible. The hull of a submarine is much stronger than that of an egg, but it can still be crushed because its internals are mostly gas $\endgroup$
    – MikeH
    Dec 18, 2018 at 16:43
  • $\begingroup$ @MikeH People aren't uniform and good at distributing stress like an egg though. We also have a lot more going on in terms of fluids and objects in the body, where an egg is just the white and yolk. I don't think showing an egg without injury is good evidence that a person would look essentially normal from the outside under high pressure. $\endgroup$
    – JMac
    Dec 18, 2018 at 17:09
  • $\begingroup$ Yes, the egg has great shape to combat a compression force,but more important is a fact that there is little gases inside and an egg shell can let it out and let the water in, without visible damage. In the experiment egg has some time to do all that. But it is a good addition information. $\endgroup$
    – Artemijs Danilovs
    Dec 18, 2018 at 18:41
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What would a death by extreme water pressure look like?

Cort Ammon's answer is quite correct, as is Andrey's. I'll add a bit more science and some idea of visuals.

  • 1000 metres depth. The pressure here is about 100 atmospheres, Cort Ammon's answer applies as-is.

  • 10,994 metres depth. Mariana Trench depth.

    the water column above exerts a pressure of 1,086 bar (atmospheres)... At this pressure, the density of water is increased by 4.96%

The eyeballs would get pushed into the skull through the optic nerve channel with a pop.

  • 600 km depth. Pressure = 60,000 bar, the density of the water is increased by ~ 16%

This is significant, at this point the pressure difference (59.7 tons per sq cm) and density difference from the outside to the inside of the skull (corresponding to an inrush of roughly 200 cc) is high enough that the pressure wave will implode the skull, and every other bone in the body, turning them to barely more than grit.

Essentially a faceless, barely-recognisable-as-human skin full of jelly, denatured proteins, fat and pulverised bones would gently settle downwards.

Refs:

https://en.wikipedia.org/wiki/Mariana_Trench

http://www1.lsbu.ac.uk/water/ice_vi.html

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  • $\begingroup$ I was actually hoping that someone would mention Mariana Trench conditions AND a lot of gore. Thanks a lot for your input. $\endgroup$
    – Magus
    Dec 18, 2018 at 11:38
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    $\begingroup$ Eyeballs pushed into the skull through the optic nerves is one hell of a way of saying "it wouldn't be much fun". Yowch. $\endgroup$
    – ceejayoz
    Dec 19, 2018 at 14:48
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Like all bizarre questions, the Mythbusters did this to a human analog skeleton and pig flesh. Here is the before picture.

enter image description here

Creepy, yep. But compared to what happens next, it is nothing. And here is the after picture.

enter image description here

Yes, that was pig flesh sealing the broken seal against the pressure gradient. Now that you have seen it, you can't unsee it. Go forth and build your world where this apparently happens to people by tossing them through an invisible barrier.

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    $\begingroup$ I remember watching that episode and when they opened it up the skull had multiple cracks. I cannot recall whether it actually broke apart though. Just as an fyi about 60% of the body went straight into the helmet based on what they said afterwards. So yeah, it was certainly bone crushing force. Might want to verify and add these details to the answer. $\endgroup$
    – user64742
    Dec 19, 2018 at 5:48
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The water rushing in at high speed are a shockwave coming in all directions. You were all correct about the air cavities in your body. They won't hold-on against the pressure and the body structure would cave-in.

Here is a demonstration: https://www.youtube.com/watch?v=W4DnuQOtA8E

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A lot like this hydrolic press crushing gummie bears with a side of exploding violently. If the pressure is great enough even your bones will disintegrate into dust, but either way you will end up like a non flammable underwater firework.

If you want to be a total cynical person, have them take surface creatures and purposefully have them crushed by the pressure and sell tickets to see it.

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