The Eastern cottonmouth (Agkistrodon piscivorus) a venomous snake, is a species of pit viper in the subfamily Crotalinae of the family Viperidae. The species is endemic to the southeastern United States. This is the world's only semiaquatic viper, usually found in or near water, particularly in slow-moving and shallow lakes, streams, and marshes.
Eastern Cotton Mouth Snake

Geoff Gallice, Gainesville, FL; via Wikimedia Commons