[robjan]

The internal pressure would have to be hundreds on atmospheres to offset the pressure outside. They would have to carry a lot more air at very high pressure on on the surface with more complicated and robust equipment to handle it. It would also make buoyancy management much harder. There's also the additional problem that there is a risk of gas narcosis above 3 atmospheres of pressure.

[noduerme]

So remember "The Abyss"? (James Cameron)... the aquanauts were living in a habitat that was pressurized at the bottom of the Mariana Trench or something. Was that just done before he realized it was physically impossible for humans to live in that kind of hyperbaric situation...? Or is it possible at any pressure with the right gas mixture?