In Slavic mythology, vodyanoy or vodyanoi (Russian: водяно́й, IPA: [vədʲɪˈnoj]; lit. '[he] from the water' or 'watery') is a male water spirit. Vodník (or in Germanized form: Hastrman), in Czech fairy tales, is the same creature as the Wassermann or nix of German fairy tales.
Vodyanoy usually appears as a middle to old aged man with some frog-like body parts. Vodyanoy lives in lakes, rivers and practically any type of water (except for seas and oceans) and can't live too long out of water. He was usually adressed as "grandfather" or "uncle" by the townspeople.
Often depicted as riding a log or a fish on the water surface, he would kidnap people and put their souls in a jar which makes them his slaves.