Water Pressure

[Bazile]

How can sea creatures withstand the enormous pressures deep in the oceans

[davebro]

the pressure inside them is the same as the pressure outside

[goodgoalie]

https://lifeoffish.com/how-do-deep-sea-creatures-survive-a-mystery-reveled/#How_do_deep-sea_creatures_survive_the_pressure_adaptation

[Old_Geezer]

A very tough outer layer & a high inside body pressure?

[Hopkirk]

They are created there and live there. Many can't cope with the reduced pressure if they are brought up to the surface

[davebro]

But what about the ones who don't live permanently at depth but frequently deep dive.

[douglas9401]

It's basic biology innit, swim bladders, pressure equalisation, controlled breathing.

None of the above would have developed if whales could hold a screwdriver or learn to write though.

[LadyCG]

Isn't it something to do with their composition being mostly water anyway?

I'm sure there are tiny creatures living deep in the Mariana Trench and even in the Challenger Deep.