Vodyanoy

водяной

In slavic mythology, vodyanoy is a male water spirit. He has a fish's tail, luminescent green eyes. Local drownings are said to be the work of the vodyanoy (or rusalkas).
When angered, the vodyanoy breaks dams, washes down water mills, and drowns people and animals. (Consequently, fishermen, millers, and also bee-keepers make sacrifices to appease him.) He would drag down people to his underwater dwelling to serve him as slaves.