Its hide was generally supposed to be black (though in some stories it was white), and will appear to be a lost pony, but can be identified by its constantly dripping mane. Its skin is like that of a seal, smooth, but is as cold as death when touched. The horse's appearance is strong, powerful, and breathtaking. Water horses are also known to transform into beautiful women in order to lure men into their traps. It is understood that the nostril of the horse is what creates the illusion of grandeur. The water horse also creates illusions to keep itself hidden, keeping only its eye above water to scout the surface, much like the illusion of a fish's pupil.
The water horse is also a common form of the kelpie, said to lure mortals, especially children, into the water to drown and eat them. It performs this act by encouraging children to ride on its back. Once its victims fall into its trap, the kelpie's skin becomes adhesive and it bears them into the river, dragging them to the bottom of the water and devouring them - except the heart or liver. A common Scottish tale is the story of nine children lured onto a kelpie's back, while a tenth keeps his distance. The kelpie chases him and tries to catch him, but he escapes. A variation on this is that the tenth child simply strokes the kelpie's nose, but when his finger becomes stuck to it he takes a knife from his pocket and cuts his own finger off. He saves himself, but is unable to help his friends as they are pulled underwater with the kelpie. Commonly known as spirits of the dead, kelpies are not benevolent creatures.
An exception is a Scottish tale in which, towards the end of the mystical period of Scotland, a water horse fails to travel to Tir Na Nog with its fellow mystic folk, and instead rises above water, seeking a wife. However, after attempting to court a clever girl, who consults the wiseman about the situation, he is captured and forced to work in order to be taught compassion. After learning his lesson, he is given the choice of departing to Tir Na Nog, or drinking a magic potion that will make him a real man. The water horse, now full of love decides to drink the potion which erases the memories of his life as a water horse and gives him the chance to live with the clever girl with whom he has fallen in love.
In Orkney a similar creature was called the nuggle, and in Shetland a similar creature was called the shoopiltee, the njogel, or the tangi. On the Isle of Man it is known as the cabbyl-ushtey or the glashtin. It also appears in Scandinavian folklore where in Sweden it is known by the name Bäckahästen, the brook horse. In Norway it is called nøkken, where the horse shape is often used, but is not its true form. In the Faroe Islands it is called Nykur and in Iceland it is called nykur or nennir. Another similar Scottish water horse is the each uisge, which also appears in Ireland.
The film Into the West features a kelpie. Ossie, the younger of the two brothers, has a kelpie come to him so as to unite the broken family of himself, his brother and father. Ossie imagines that the kelpie is his mother's soul. The kelpie is a white mare, who true to her nature can jump amazing lengths and heights. Also true to her nature, she nearly lures Ossie to a watery grave, recalling the kelpie legend as well as the legend of Ossian's Ride. However Ossie is saved by the ghost of his mother, and the love of his brother and father.
Kelpie is also a family name found around north-west Ireland and parts of Scotland, although in relatively small numbers. Genealogical research by the Irish Kelpies suggests that their ancestors travelled from Scotland around 1760 to farm in Co. Donegal,Ireland.