"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. One way to tell apart a cottonmouth and Northern water snake is to get a good look at their mouth - if it's white, stay away! If it's not, you'll live to see another day.