Inspired by a Song by the group "Toad in the Hole" I rather like it. The Each-uisge was a water horse not too unlike the kelpie that usually took the form of a black horse and waited by deep pools. If an unweary traveler tried to mount the black steed it would punge into the waters, it's coat was adhesive and drown it's victim,devouring all but the liver, which would wash to shore. It sometimes also took the form of a handsome man or woman, with water vegitation caught in their hair.