Common Name: Diamond-backed water snake Scientific Name: Nerodia rhombifer Identification: 18-65 in. Gray-brown or tan with dark gray or brown crossbands alternating on the back and sides; belly yellowish with small dark markings. Scales keeled Habits: Diamond-backed water snakes occur in and around lakes, ponds, marshes, swamps and larger streams and rivers, usually in low country. Distribution: Throughout Louisiana, but uncommon in uplands. Comments: The Diamond-backed water snake is most often confused with the water moccasin, which usually does not attain the same length. The water moccasin is also a thicker, as well as shorter, snake. The diamond backed water snakes are not venomous.