The Uruisg, often confused with the brownie, haunts lonely places and waterfalls, and, according to his mood, helps or harms the wayfarer.  His appearance is that of a man with shaggy hair and beard.[631] In Wales the afanc is a water-monster, though the word first meant “dwarf,” then “water-dwarf,” of whom many kinds existed.  They correspond to the Irish water-dwarfs, the Luchorpain, descended with the Fomorians and Goborchinn from Ham.[632]

In other cases the old water beings have a more pleasing form, like the syrens and other fairy beings who haunt French rivers, or the mermaids of Irish estuaries.[633] In Celtic France and Britain lake fairies are connected with a water-world like that of Elysium tales, the region of earlier divinities.[634] They unite with mortals, who, as in the Swan-maiden tales, lose their fairy brides through breaking a tabu.  In many Welsh tales the bride is obtained by throwing bread and cheese on the waters, when she appears with an old man who has all the strength of youth.  He presents his daughter and a number of fairy animals to the mortal.  When she disappears into the waters after the breaking of the tabu, the lake is sometimes drained in order to recover her; the father then appears and threatens to submerge the whole district.  Father and daughters are earlier lake divinities, and in the bread and cheese we may see a relic of the offerings to these.[635]

Human sacrifice to water-divinities is suggested by the belief that water-monsters devour human beings, and by the tradition that a river claims its toll of victims every year.  In popular rhymes the annual character of the sacrifice is hinted at, and Welsh legend tells of a voice heard once a year from rivers or lakes, crying, “The hour is come, but the man is not."[636] Here there is the trace of an abandoned custom of sacrifice and of the traditional idea of the anger of the divinity at being neglected.  Such spirits or gods, like the water-monsters, would be ever on the watch to capture those who trespassed on their domain.  In some cases the victim is supposed to be claimed on Midsummer eve, the time of the sacrifice in the pagan period.[637] The spirits of wells had also a harmful aspect to those, at least, who showed irreverence in approaching them.  This is seen in legends about the danger of looking rashly into a well or neglecting to cover it, or in the belief that one must not look back after visiting the well.  Spirits of wells were also besought to do harm to enemies.

Legends telling of the danger of removing or altering a well, or of the well moving elsewhere because a woman washed her hands in it, point to old tabus concerning wells.  Boand, wife of Nechtain, went to the fairy well which he and his cup-bearers alone might visit, and when she showed her contempt for it, the waters rose and destroyed her.  They now flow as the river Boyne.  Sinend met with a similar fate for intruding on Connla’s well, in this case the