Kelpies

Near Falkirk in Scotland.
A kelpie is a malevolent Scottish magical being that can take many forms, often a horse or a young woman.
They are particularly attractive to children – but they should take care, for once on its back, its sticky magical hide will not allow them to dismount! Once trapped in this way, the kelpie will drag the child into the river and then eat him.
These water horses can also appear in human form. They may materialize as a beautiful young woman, hoping to lure young men to their death. Or they might take on the form of a hairy human lurking by the river, ready to jump out at unsuspecting travellers and crush them to death in a vice-like grip.