As long as there are no hollow components, such as lungs, then pressure is not really a problem. The solution is to allow the internal cell pressure match the environment. Under these circumstances there is no net pressure on the cell membranes and the organism will be unaffected. Of course, if you bring it to the surface too quickly it will explode, since the internal pressure is still high.

Hence, one of the functions of SCUBA diving equipment is to regulate the pressure of the gas that the diver breathes in. As he descends, the air mix that he inhales must be at a greater pressure so that he is able to breathe. A free diver (who holds her breath) experiences huge pressure on her ribcage so her lungs shrink to a fraction of their normal volume.