The Amazonian Marsh Rat uses waterside habitats and wet grasslands. Coat color and reported range vary, and the older broad species account includes records that its authors considered uncertain.
The back is buff to reddish brown with black hairs mixed in; the underside is paler. The hind feet are partly webbed.
Venezuelan accounts describe use of grassland, marsh, and cultivated waterside habitats such as rice fields. Its body is adapted to swimming, but diet and behavior records are local to the studies cited.
An extinction-risk assessment has not been added yet.