Later Celtic folk-belief associated monstrous and malevolent beings with rivers and lakes.  These may be the older divinities to whom a demoniac form has been given, but even in pagan times such monstrous beings may have been believed in, or they may be survivals of the more primitive monstrous guardians of the waters.  The last were dragons or serpents, conventional forms of the reptiles which once dwelt in watery places, attacking all who came near.  This old idea certainly survived in Irish and Highland belief, for the Fians conquered huge dragons or serpents in lochs, or saints chained them to the bottom of the waters.  Hence the common place-name of Loch na piast, “Loch of the Monster.”  In other tales they emerge and devour the impious or feast on the dead.[623] The Dracs of French superstition—­river monsters who assume human form and drag down victims to the depths, where they devour them—­resemble these.

The Each Uisge, or “Water-horse,” a horse with staring eyes, webbed feet, and a slimy coat, is still dreaded.  He assumes different forms and lures the unwary to destruction, or he makes love in human shape to women, some of whom discover his true nature by seeing a piece of water-weed in his hair, and only escape with difficulty.  Such a water-horse was forced to drag the chariot of S. Fechin of Fore, and under his influence became “gentler than any other horse."[624] Many Highland lochs are still haunted by this dreaded being, and he is also known in Ireland and France, where, however, he has more of a tricky and less of a demoniac nature.[625] His horse form is perhaps connected with the similar form ascribed to Celtic water-divinities.  Manannan’s horses were the waves, and he was invariably associated with a horse.  Epona, the horse-goddess, was perhaps originally goddess of a spring, and, like the Matres, she is sometimes connected with the waters.[626] Horses were also sacrificed to river-divinities.[627] But the beneficent water-divinities in their horse form have undergone a curious distortion, perhaps as the result of later Christian influences.  The name of one branch of the Fomorians, the Goborchinn, means the “Horse-headed,” and one of their kings was Eochaid Echchenn, or “Horse-head."[628] Whether these have any connection with the water-horse is uncertain.

The foaming waters may have suggested another animal personification, since the name of the Boyne in Ptolemy, [Greek:  bououinda], is derived from a primitive bou-s, “ox,” and vindo-s, “white,” in Irish bo find, “white cow."[629] But it is not certain that this or the Celtic cult of the bull was connected with the belief in the Tarbh Uisge, or “Water-bull,” which had no ears and could assume other shapes.  It dwells in lochs and is generally friendly to man, occasionally emerging to mate with ordinary cows.  In the Isle of Man the Tarroo Ushtey, however, begets monsters.[630] These Celtic water-monsters have a curious resemblance to the Australian Bunyip.