A bandit or brigand.
A petty thief or waterfront ruffian.
A member of the water police.
The European water vole, Arvicola amphibius, formerly Arvicola terrestris.
A water mouse, especially, the rakali, Hydromys chrysogaster.
Any of various aquatic or semi-aquatic rodents from Florida and southern Georgia, especially Neofiber alleni; the muskrat.
A person fond of water sports.