The nuckelavee or nuckalavee is a horse-like demon from Orcadian folklore that combines equine and human elements. British folklorist Katharine Briggs called it "the nastiest" of all the demons of Scotland's Northern Isles. The nuckelavee's breath was thought to wilt crops and sicken livestock, and the creature was held responsible for droughts and epidemics on land despite being predominantly a sea-dweller.

A water horse is a mythical creature, such as the Ceffyl Dŵr, Capaill Uisce, the bäckahäst and kelpie.