It´s because the level gets more dangerous and vandalized the farther you go, and this is a picture of the eroded state. It just gets worse and worse, fish are part of it I guess, probably because this shows a sign of oldness.
Damnation; You brought yourself here. Why did you leave level 11? It seems that you just wanted to bring an end to yourself. The rest of your pathetic existence will consist of regret...