The Water Moccasin is one of the most deadly snakes in North America. It is a pit viper in the same family as the Copperhead and Rattlesnake. It has a brown, olive or black upper body with a light yellow belly. Distinct crossbands extend all the way around and across the belly. The Cottonmouth gets its name from the white inner surface of its mouth which it exposes when approached. They are an average length of 30 inches, rarely growing to over six feet.