Any of 65–80 snake species of the genera Natrix and Nerodia , as well as similar snakes of the family Colubridae, found worldwide except in South America.
Most species have a stout body with dark blotches or streaks and ridged scales. Some are simliar in appearance to venomous species. They kill fishes and amphibians with a nonvenomous bite. The New World species live in or near water and bear live young; European species are less water-dependent and lay eggs. In defense they inflate the head, strike, and release a foul secretion. Average length is about 3 ft (1 m); some Old World species reach 6 ft (1.8 m).