The kelpie is usually described as a powerful and beautiful black horse inhabiting the deep pools of rivers and streams of Scotland, preying on any humans it encounters. One of the water-kelpie's common identifying characteristics is that its hooves are reversed as compared to those of a normal horse, a trait also shared by the nykur of Iceland. An Aberdeenshire variation portrays the kelpie as a horse with a mane of serpents, whereas the resident equine spirit of the River Spey was white and could entice victims onto its back by singing.
https://en.wikipedia.org/wiki/Kelpie