The term 'LOON's Cousin' is a crossword solution for the word GREBE, which is a five-letter waterbird. Grebes are members of the Podicipedidae family and are closely related to loons, which are also members of the same family. They are found in freshwater and coastal habitats around the world and have a distinctive pointed bill and lobed feet. Grebes are excellent swimmers and divers, and they feed on small fish, crustaceans, and aquatic insects.