The viperine water snake or viperine snake (Natrix maura) is a semiaquatic, fish-eating natricine water snake. Despite its common names, it is not a member of the subfamily Viperinae. It was given its common names due to exhibiting a dorsal colour pattern that superficially resembles that of sympatric adder species. In comparison to other Natrix species its head is also somewhat wider and more distinct from the neck. Like most members of the Natricinae it possesses a venom gland on each side of the upper jaw (Duvernoy's gland) that produces a mild venom that may play a role in swallowing or digestion. The gland is not associated with an enlarged specialized tooth and the venom as to be applied by chewing. The species usually does not bite as a mean of defense, and the effect of a bite would be harmless to humans.