water-rat

Noun

water rat (plural water rats)

1. (US) Any of various aquatic or semi-aquatic rodents from Florida and southern Georgia, especially Neofiber alleni; the muskrat.
   • Otters are even harder to spot; the coypu, a North American water rat, is more commonly seen.2004, James McConnachie, Rough Guide to the Loire, page 43
2. (Australia) A water mouse, especially, the rakali, Hydromys chrysogaster.
   • "There [...] you will find the water-hole that is sacred to Biggoon, the giant water rat."1943, H. Lorna Bingham, The Lost Tribe, Sydney: Winn and Co., page 11, column 1
3. (informal) A European water vole (Arvicola amphibius, formerly Arvicola terrestris).
4. (US, slang) A petty thief or waterfront ruffian.
5. (slang) A person fond of water sports.
6. (Australia, slang) A member of the water police.