The Ucayali water rat is a semiaquatic rodent recorded in Peru and Ecuador. Its hind feet are broadly webbed, and specimens have been captured along forest streams.
Its hind feet have extensive webbing, its whiskers are long, and its dorsal fur is longer than that of the related genus Nectomys. The underside is whitish.
Peruvian specimens were captured along streams in primary forest. The authors suggest it may also use seasonally flooded forest, but they caught none there.
An extinction-risk assessment has not been added yet.