Undine

"Most artistic of all the continental weird tales is the German classic Undine (1814), by Friedrich Heinrich Karl, Baron de la Motte Fouqu. In this story of a water-spirit who married a mortal and gained a human soul there is a delicate fineness of craftsmanship which makes it notable in any department of literature, and an easy naturalness which places it close to the genuine folk-myth." -- H.P. Lovecraft, "Supernatural Horror In Literature"