Killer Croc used to be a guy that got this rare disease in the jungle that made his skin green and let him breath under water, I think. He blamed Batman for it and became one of his nemises. His powers include:breathing under water, living in the sewers and having camoflage. These make him kind of one of the enemies the Dark Knight REALLY has to look out for, others being The Scarecrow, The Joker, Bane, Gorilla Grodd and Lex Luthor. Even though he can breath underwater he has a speedboat at his disposal. He has a small rapid-fire pistol.