Water viper
Agkistrodon piscivorus, also known as the cottonmouth snake, water moccasin, or water viper, is a species of highly venomous pit viper (a type of snake) found throughout southeastern United States. Commonly called cottonmouths because of their all-white mouth, they are often confused with Northern water snakes, which are harmless, but the cottonmouth is much the opposite.