The banded water snake or Southern water snake (Nerodia fasciata) is a species of mostly aquatic, nonvenomous, colubrid snake found in the central and southeastern United States, from Indiana, south to Texas and east to Florida.
The Southern water snake grows from Template:Convert to Template:Convert, and is typically gray, green-gray or brown in color with dark cross-banding. Many specimens are so dark in color their patterning is barely discernible. They have a flat head, and are fairly heavy bodied. Their appearance leads them to be frequently mistaken for other snakes with which they share a habitat, including the less common cottonmouth.
The species is ovoviviparous.
There are three recognized subspecies of N. fasciata:
- Nerodia fasciata confluens (Blanchard, 1923)
- Nerodia fasciata fasciata (Linnaeus, 1766)
- Nerodia fasciata pictiventris (Cope, 1895)