Fordonia leucobalia is an aquatic snake known by the common names crab-eating water snake and white-bellied mangrove snake. It is a common resident of mangrove swamps and tropical tidal wetlands from coast of Southeast Asia to Indonesia and the coasts of Northern Australia. Individual F. leucobalia reach up to a meter in length, and are brown or gray in color with a white belly. There is significant color variation. Some have spots. The anatomy reflects the snake's water-living lifestyle: the eyes are located atop the head, and the nostrils have valves that close when the snake dives.