Soft bodied fish like the snail fish can apparently live at depths deeper than 25,000 feet… yet somehow, despite modern engineering marvels, and the availability of the strongest materials available to man, we can barely create underwater vehicles that dive to the same depths — and even the ones that do, are far from safe. How do these submarines get crushed and these soft bodied fish survive?
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It’s not the pressure that’s the problem; it’s the pressure *difference* that’s the problem. Submarines have hollow, low-pressure air-filled spaces inside them; the fish don’t. The submarines must maintain their low pressure spaces through the sheer strength of their mechanical structure; the fish do not face this challenge because they simply have the same pressure inside and out. This wouldn’t be a problem for humans either if we could fill our hollow spaces with liquid—but that tends to hamper our ability to breathe.
Take a can of soda and try and squeeze it, how does that go? Maybe a tad? Now pop the top and drink the soda and squeeze the can, how about now? Much different right?
Fish have one thing those submarines don’t – they are filled with water.
Water is pretty much not compressible as a thing on Earth, meaning you can’t really squeeze it into a smaller space with the kind of forces we experience. Air though, air can be squeezed (checks notes) a fucking ton.
Unfortunately for them, submarines are filled with air, that means they are really squuuueeeezeable for the water around them. But deep see fish are mostly water-goo, you can’t really squeeze down a deep sea fish more than just water-goo.
But do the opposite – take a deep sea fish up to our pressure – you get gross explosion of water-goo.
Turning [this](https://www.nationalgeographic.com/animals/fish/facts/blobfish) into [this](https://www.dispatch.com/story/business/information-technology/2013/09/14/all-abuzz-blobfish-hooks-ugliest/23542983007/)
Because those fish evolved at that depth and their bodies are at the same pressure as the water at the depth. It’s not really about the pressure, it’s about the *difference* in pressures.Submarines carry humans, and since humans did NOT evolve at the depth, our bodies cannot withstand that pressure, so we need a pressure vessel that can protect us. This means the vessel has to withstand the enormous pressure *difference* between the inside, which is the same pressure as sea level because that’s where the people are, and the ambient pressure outside which dramatically increases as you descend.
Because the internal pressure of those fish is similar to their environment.thats why the blob fish looks like that when you take them to the surface. They don’t look like when in the deep sea. They “explode” when you take them to the surface.
Submarines on the other hand need to be full of air because humans need to survive in the submarine. It’s essentially a giant hollow tube just begging to be crushed by the pressure.
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