The first water horse, or hippocampus, was a fabled sea animal from Greek mythology. It was found in classical myth. It resembles a horse with the hind parts of a fish or dolphin. The chariot of Poseidon (the sea god) was drawn by a hippocampus. The name comes from the Greek hippos, horse; and kampos, sea monster. There are many books available on the fascinating subject of Greek mythology. Even the basis for the idea of artificial intelligence can be found in Greek myths, since intelligent machines and artifacts are mentioned in the texts.
The Each Uisge (pronounced "ech ooisky" ) - each = horse, usige = water (like whisky) is the fiercest and most dangerous of the Scottish water spirits. While the Kelpie lived in running water, the Each Uisge lived in the sea, sea lochs and fresh-water lochs. In Ireland its equivalent was called the Aughisky.
Like the Kelpie, the Each Uisge would take the shape of a fine horse or pony and stand near the water's edge. If anyone tried to ride it, it would immediately plunge into the deepest part of the loch. The water horse's coat is adhesive so that the rider cannot get off. Once it has drowned its catch the water horse devours the body, eating everything except the liver, which eventually washes up on the shore - so that everyone will know the monster has claimed another victim.
As well as human victims the Each Uisge also ate cattle and sheep, and could be lured from the water with the smell of roasted meat and then killed.
In modern times the "white horses" on the wavetops still stir the imagination.....
And look at these fantastic white river horses charging to destroy the black riders - in the movie they appear so briefly you think you must have imagined them, but they were there...
CELTIC WATER HORSES - THE KELPIE AND THE EACH UISGE
The Kelpie is a water spirit inhabiting deep pools in Scottish streams and rivers. It normally takes the form of a small horse - sometimes said to be black, but also "green as glass" with a jet black mane and tail. The Kelpie can also take the form of a human, but it always has something of the water which gives it away - like waterweed in its hair. In its horse form it might wait near a ford to tempt a weary traveller to ride it across the river. It would look like a gentle pony, but anyone foolish enough to mount it would be carried off into the river and drowned.
Another name for the kelpie on the Isle of Man is the Glashtyn. Like all kelpies, the Glashtyn appears as a horse - specifically, a grey colt. It is often seen on the banks of lakes and appears only at night.
In Ireland, a faerie known as the Phooka is also said to take the shape of a horse and induces children to mount him. He is then said to plunge with them over a precipice killing them.
Kelpies were also well known for stealing human girls to take as wives, never to see their families again. There is a story of a Kelpie's wife who managed to escape to dry land again, leaving the Kelpie and their baby son. Although she wept to leave her child, she longed for human company, and she knew the Kelpie loved his son and would care for him. She returned to her family who were overjoyed to see her again, thinking that she had been drowned years ago. But as they celebrated, a dreadful storm blew up, with howling winds and lashing rain. Above the noise of the storm they could hear the furious screams of the Kelpie. In the middle of the night, when they storm was at its worst, they heard a loud thump against the door of the house. They did not dare look, in case it was the Kelpie come for his wife. But in the morning the storm abated, and they opened the door to see what had crashed into it in the night... It was the severed head of the baby son.
Some say the kelpie is not always male, but may also take the form of a human woman. In this instance, the kelpie is often referred to as a water wraith and is most often seen clothed in a green dress. She is just as treacherous as a male Kelpie.
The original of the picture "Beware" and more by the same artist are at Elfwood - here
There was one way in which a Kelpie could be defeated and tamed; the Kelpie's power of shape shifting was said to reside in its bridle, and anybody who could possess such a bridle could force the Kelpie to submit to their will. A Kelpie in subjugation was highly prized, it had the strength of at least 10 horses and the endurance of many more, but the fairy races were always dangerous captives especially those as malignant as the Kelpie. It was said that the MacGregor clan were in possession of a Kelpies bridle, passed down through the generations from when one of their clan managed to save himself from a Kelpie near Loch Slochd.
The one in the old drawing looks like a wild, unmanageable creature, but the little ship ornament looks pretty cute.