The term 'water-dwelling rodent' refers to the NUTRIA, a large semi-aquatic rodent native to South America. It is also known as the coypu, and is characterized by its webbed hind feet and long rat-like tail. Nutrias are herbivores, and feed on aquatic plants, grasses, and other vegetation. They are considered an invasive species in many parts of the world, and can cause significant damage to wetlands and other ecosystems.