Agkistrodon piscivorus is a species of pit viper in the subfamily Crotalinae of the family Viperidae. It is the world's only semiaquatic viper, and is native to the southeastern United States. It is the only venomous species of North America's water snakes and one of 21 venomous snakes in the United States. As an adult, it is large and capable of delivering a painful and potentially fatal bite. When threatened, it may respond by coiling its body and displaying its fangs. Individuals may bite when feeling threatened or being handled in any way. It occurs in or near water, particularly in slow-moving and shallow lakes, streams, and marshes. It is a strong swimmer and has even been seen swimming in the ocean. However, it is not fully marine, unlike true sea snakes. It has successfully colonized islands off both the Atlantic and Gulf coasts.
