Thank you. 

That describes a fair portion of the lore of the Vodyanoi. The appearance is not always likethat, though. They are water spirits that are somewhat demonic. Usually looking like some combination of human and fish. The definitely have a malicious streak. But they also have mercy at times They seem tough and enterprising in the lore I found. There's even an old Russian charm to win a fist fight by calling on the blessings of the local Vodyanoi (water spirits) and Leshiy (forest spirits). 

The Rusalka are sometimes like mermaids or sirens and other times like water harpys. 

And Vodniks are water goblins who often have a lot of magic and more amphibian than fishy appearances. These tend to seem more wise and magical than the tough and often hard hearted Vodyanoi. 

And then there are Topyeltse (spelled Topielce in polish) or Drowners. These are essentially the ghosts, or occasionally undead corpses, of those who have drowned and now live solely to drown others. 

Those are the main Eastern European aquatic spirits insofar as I know.