Also found in Mermaid and Other Water Spirit Tales From Around the World...
A VERY beautiful mermaid became so much enamoured of a young man who used to tend his sheep upon the rocks, that she would frequently sit down by him, bring him pieces of coral, fine pearls, and what were yet greater curiosities, and of infinitely more value, had they fallen into the hands of a person who knew their worth, shells of various forms and figures, and so glorious in their colour and shine, that they even dazzled the eye that looked upon them. Her presents were accompanied with smiles, pattings of the cheek, and all the marks of a most sincere and tender passion. One day throwing her arms more than ordinarily eagerly about him, he began to be frightened that she had a design to draw him into the sea, and struggled till he disengaged himself, and then ran a good many paces from her; which behaviour she resented so highly, it seems, that she took up a stone, and after throwing it at him, glided into her more proper element, and was never seen on land again. But the poor youth, though but slightly hit with the stone, felt from that moment so excessive a pain in his bowels, that the cry was never out of his mouth for seven days, at the end of which he died.—Waldron.
Moore, A[rthur] W[illiam]. The Folk-lore of the Isle of Man: Being an Account of Its Myths, Legends, Superstitions, Customs, & Proverbs. London: D. Nutt, 1891.