Nixes

Nixes are water spirits who live in lakes and rivers. They are beautiful humanoid creatures who are often depicted with green teeth and fish's tails. However, they can assume many forms, including that of humans. In human shape, they can always be recognized by the permanently wet hem of their clothing. They are known to lure humans into the water--they often steal humans for spouses. Nixes are also known to dance on the water just before a human drowns there.

Sources

Kneightley, Thomas. The World Guide to Gnomes, Fairies, Elves, and Other Little People. New York: Avenel Books, 1978.

Encyclopedia Mythica: Nixes