Sahuagin
Sahuagin are a race of evil aquatic humanoids from Dungeons & Dragons. Rapacious predators who consider it their manifest destiny to conquer the oceans, they are known as the sea-devils and as shark-men for their malevolent "shark-like" personality, violent hatred of weakness and infirmity, rampant cannibalism, and ability to commune with sharks, although in terms of looks they more closely resemble the Creature from the Black Lagoon with a tail. They were one of the "big races" in Advanced Dungeons & Dragons; like Orcs, they received a huge entry in the Monster Manual, and went on to have their own book in the Monstrous Arcana series, called "The Sea Devils". Unlike Orcs, they have a more Nazi-esque mentality, with everyone knowing their place and working for the greater good (well, greater evil), and so they have a racial alignment of Lawful Evil.
Notorious for their propensity to have mutations; four-armed sahuagin are extremely common and usually rise to the highest positions (those seven attacks are a killer!) and the infamous malenti are sahuagin who perfectly resemble sea elves