The Water Mongoose has an overall length of 1000mm and is robust in stature. The Water Mongoose weighs up to 4.2kg. The Water Mongoose has a dark brown, waterproof coat with a lighter coloured nose. Water Mongoose has a large head that accommodates a larger brain. The larger brain gives the Water Mongoose increased muscular control and tactile sensitivity.
The Water Mongooses diet consists mainly of crab, prawn, fish and on some occasions frogs. When on land, they hunt rats, blue duiker and cane rats.
The Water Mongoose give birth to a litter containing 2 young after their gestation period ends. Water Mongoose can give birth to more than one litter a year. Little is known about the sexual behaviour of the Water Mongoose other than that they breed twice a year. The female will prepare a nest in a hole in swampy areas.
Water Mongoose have solitary habits and is a semi aquatic and nocturnal species. These animals have regular habits that and follow clearly defined and smooth pathways to rivers, shorelines and are often hidden by tall grass and reeds. Water Mongoose have a rather strange way of catching birds. They will lay on their backs to imitate sunbathing, with their brightly coloured anus sticking out and taking prominence between the dark fur. It is assumed that the colour attracts birds to peck at the area. As the bird gets close, the mongoose will ambush the bird. Mongoose have a strange self defence mechanism where they release a foul brown liquid from their anal sacs when they are threatened or cornered.
Water Mongoose are associated with rivers, streams, estuaries and coastal areas as well as vleis and reedbeds.