Water Grandfather...

The Russian "Water Grandfather" or Dyedushka Vodyanoy is a dangerous ogre. He is an adroit shapeshifter and is said to drown people who swim at midnight or noon. He inhabits the deeps of rivers, streams, and ponds. By day he remains concealed, like an old trout or salmon. By night he surfaces to drive is subaqueous cattle, sheep, and horses ashore to graze. In the winter he smashes ice along the rivers, piling up great blocks. Mill wheels he is amused to destroy. But in a favorable mood he drives the fish into the fisherman's net or gives a warning of coming floods. His beautiful daughters, tall, pale, with an air of sadness, transparently costumed in green, torture and torment the drowned. They rock in the trees beautifully singing.