Kelpie

In Scottish folklore, a kelpie, or water kelpie, is a mythical shape-shifting spirit inhabiting lochs in Scotland. They also inhabit meres and streams in Yorkshire (Jórvik) mythology. Legends of these shape-shifting water-horses, under various names, spread across the British Isles, appearing in the Northern Isles, Irish, Manx, Northern English, and Welsh folklore. It is usually described as a grey or white horse-like creature, able to adopt human form. Some accounts state that the kelpie retains its hooves when appearing as a human, leading to its association with the Christian idea of Satan