The Water Opossum ( Chironectes minimus ) , also locally known as the Yapok , an aquatic marsupial are member of the opossum family with black and gray waterproof fur , webbed hind feet and a backward-pointing pouch in both sexes . The Water Opossum ( Chironectes minimus ) , also locally known as the Yapok , is a marsupial of the family Didelphidae .