There is a horizontal dark line behind the eye, and a light band across the back of head. There are no dark markings on the labial scales. The belly is tannish to pinkish, with black dots along the edges. The scales are keeled , and there are 15-17 dorsal scale rows at midbody. The pupil is round.
Juveniles are dark brownish with a light band across back of head.
In Florida, it is found only in the extreme western panhandle. Outside of Florida, it is found from southern Alabama to southern Texas. Uncommonly found in the western Florida panhandle's estuaries, marshes, and prairies. The marsh brown snake is active during the day, but may be seen at night during warm weather. It is a terrestrial burrower, occasionally found under driftwood along the Gulf coast.