system
Given the following post, respond as if you're commenting on Reddit:
human
How can deep sea creatures withstand the immense pressure? What’s different in structure between them and humans for example, that allows them to stay unaffected?
gpt
Mechanically, human bodies are capable of withstanding the immense pressure at the bottom of the sea. Our bodies are mostly water, which is an incompressible liquid. Most of our pressure-sensitivity problems come from the gasses (oxygen, nitrogen) in our bodies. 

There are three big reasons we don't have skin divers walking around on the ocean floor:

1. It's cold down there

2. The transition from high pressure (deeper) to lower pressure must be slow and carefully managed. Oxygen and nitrogen gas becomes more soluble in water at high pressure. As you come up from the sea floor the oxygen and nitrogen become less soluble and you have gas pockets trapped in your body, and then as you continue to rise the pressure lessens and those gas bubbles expand inside your body, causing a variety of different kinds of damage. This is known as decompression sickness a.k.a. "the bends." Divers must ascend slowly to avoid this, and it would end up taking hours to do so safely from the sea floor.

3. Last, and biggest, is that high pressure does affect our body chemistry. As with before, the pressure affects the gasses in our body more than anything else. At high pressures nitrogen and other gasses become a narcotic and this affects your cognition as though you were drunk. We can mitigate this to some extent with different gas mixtures in a breathing tank, but then above a certain pressure simple oxygen becomes toxic. The oxygen becomes more reactive with things it shouldn't react with, in particular the tissues of the nervous system, and seizures can result. Seizures occurring underwater generally lead to death by drowning.

So to answer your question directly- deep sea creatures withstand the pressure because they are mostly made up of water. Water is an incompressible fluid so it doesn't react much to high pressures. The bigger advantage for deep-sea life is a different body chemistry that's functional at those depths.