Why do deep sea fishes disintegrate if you bring them to the surface?

[Angelo V]

What kind of transformation occur to thier bodies?

[Cyrus L]

Deep sea fish must have high internal pressure built up in the body, due to the high pressure in the deep sea. Or else they will be "squeezed" in the deep water.

When they come to shallow, the shallow water exerts much less pressure than the deep water on the fish. Thus the internal pressure from the fish is much high than the external environment. The fish is not necessary to explode but they die very soon since the organs are damaged badly, together with some metabolic activities.