At almost 2 meters long and weighing 30 kg, the giant otter is the largest otter in the world, the only species of its genus. It has a white patch on its neck that is unique to each individual. Its webbed feet, along with its strong tail, allow it to move easily in the water. Its long whiskers help it detect food underwater, and its thick fur prevents its skin from getting wet. When submerged, it closes its ears and nostrils to keep water out.

It builds its burrow among the vegetation located on the banks of rivers or in marshy areas, where it spends the day searching for crabs, small mammals, birds, fish and reptiles.

This is a social species, forming family groups of up to eight members. Litters range from one to five young, and parents teach the young to hunt through play. It has no natural predators, with habitat degradation and loss being its main threat. Between 1950 and 1960, the population declined dramatically due to hunting for its fur, which is now prohibited. Guyana is the last major reservoir for this species.