Hermaphrodite the handsome son of Hermes and Aphrodite, was the great-grandson of Atlas, whence called by the patronymic Atlantius. (He was raised like his grand-father by the nymphs of Mount Ida.) As a young man he wandered through the hot woods one day; lying down beside the well of the Naiad Salmacis. Apparently the spring-goddess did not possess the bewitching beauty or wilily ways of the water nymphs above. This daughter of the River Meander fell in love with Hermaphrodite. He failed to appreciate her charms, but found her waters charming. As he slipped naked into their embrace, Salmacis prayed to the gods that they might remain united forever. Some god granted the request, and when Hermaphrodite rose dripping from the well rather than the tan muscular frame, he found his body white and soft with swelling breasts upon his chest Hermaphrodite’s, anger was so great that a cursed laid ever after on the well, that whatever manly man bathed there would find himself emasculated. A vaguely similar tale tells about Narcissus at a well and another love sick nymph, but the poets (Homeric Hymn 19 to Pan 1) tells us the nymph in question was an oread.
So in general, young heroes and hairy satyrs stumbling across a limpid pool of hydriades might end up enjoying himself, one way or the other, possibly as the boy-toy of a group of goddess immortal and forever young. Though hunter's stumbling across other classes of classical nymphs haven't scored so well. Heroic hunters coming across a refreshing spring and a love sick nymph might not end up living happily everafter, but the nymph in question might end up disappearing. With Hydriades and minor goddesses of a more sinister sort, apparently failing in their seductive water-based role can have fatal consequences.
All images thanks to Wikipeida.