The boobrie is a mythological shapeshifting entity inhabiting the lochs of the west coast of Scotland. It commonly adopts the appearance of a gigantic water bird resembling a cormorant or great northern diver, but it can also materialise in the form of various other mythological creatures such as a water bull.
A generally malevolent entity, the boobrie typically preys on livestock being transported on ships, but it is also fond of otters, of which it consumes a considerable number. In its manifestation as a water horse the creature is able to gallop across the top of lochs as if on solid ground. During the summer months it is seen infrequently as a large insect, sucking the blood of horses.
Folklorist Campbell of Islay has speculated that descriptions of the boobrie may be based on sightings of the great auk. The bellowing sound made by the boobrie, more like a bull than a bird, may have its origin in the strange call of the common bittern, which was a rare visitor to Scotland.