Some snakes display a thin, white line between the pale belly and their darker top scales.

[7] Plain-bellied water snakes are found in every southeastern state of the U.S., except for the higher elevations in the Appalachian Mountains (thus excluding them from eastern Tennessee and western North Carolina).

The snakes are almost always found near a permanent freshwater source, usually several feet deep, and not necessarily clear or fast-moving waters, either.

In their natural geographic range, the snakes are adapted to a wetland lifestyle, often found at or near creeks, rivers, swamps, floodplains, lakes, and ponds, as well as man-made reservoirs, dams, and canals.

In warmer months, they are typically found basking on logs or near bodies of water, swimming, or traveling over land.

They feed primarily on tadpoles, small amphibians, fish, crayfish and other crustaceans,[10] aquatic insects (like water beetles), hatchling turtles and carrion.

[10] Because of the amount of time they spend on land, the snake's diet includes a large quantity of amphibians, consisting mostly of toads and frogs.

However, in 2010, Makowsky, et al. determined that there was "little support for the recognized subspecies as either independent evolutionary lineages or geographically circumscribed units and conclude that although some genetic and niche differentiation has occurred, most populations assigned to N. erythrogaster appear to represent a single, widespread species.

"[12][13] The plain-bellied water snake is considered a conservation risk because of loss of wetlands and other anthropogenic factors.