He hasn't had a lot of ink devoted to him in the comics, but the alternate universe evil-version of Aquaman is usually described as a humanoid fish creature called "Barracuda" who attacks and pillages Earth-2 when the Crime Syndicate of Amerika is otherwise preoccupied.

He is sometimes described as being a blue-skinned merman, but attached at the bottom is a gold-skinned version from his 2005 appearance in JLA. I suppose my version falls somewhere in between.

When I was young, Earth-2 used to be called Earth-3, and since this Earth is sometimes called Anti-Matter Earth.