The Atlantic salt marsh snake is a slender, heavily keeled water snake about 2 feet in total length, with a pattern of stripes that are variously broken into blotches. The dorsal ground color is pale olive, patterned with a pair of dark brown stripes running down the back and enclosing a pale mid-dorsal stripe. These dark stripes usually become fragmented posteriorly into a series of elongate blotches. There is also a row of dark blotches along the lower sides of the body, which merge to form stripes in the neck region. The ventral surface is black with a median series of yellowish spots. This snake feeds on small fish in shallow water. It is most active at night, during periods of low tide.
