Northern water snake The belly also varies in color. It can be white, yellow, or gray. Usually it also has reddish or black crescents. The northern water snake is nonvenomous and harmless to humans, but superficially resembles the venomous cottonmouth and is often killed unnecessarily as a result of this mistaken identity. The two can be easily distinguished by morphological traits: the water snake has a longer, more slender body and a flattened head the same width as the neck, round pupils, and no heat-sensing pits. The cottonmouth has a fatter body, a wedge-shaped head with prominent venom glands that are wider than
Green water snake giving the appearance of a ring of small plates around the eye, a character shared only with the species "N. floridana". A heavy-bodied snake, "N. cyclopion" is dark green, olive, or brown dorsally. Ventrally, it is yellowish on the anterior third, and the on remainder dark brown with yellow or white semicircles. "N. cyclopion" averages 76–140 cm (30-55 inches) in total length (including tail). "N. cyclopion" prefers still waters such as bayous, lakes, marshes, ponds, sluggish streams, and swamps. It is sometimes found in brackish water. The green water snake preys upon crayfish, frogs, and fish. The former subspecies, "Nerodia