Undines

Undines (Lat. unda, 'wave'), the name given in the fanciful system of the Paracelsists to female water-spirits. They intermarry readily with human beings, and the Undine who gives birth to a child under such a union receives with her babe a human soul. But the man who takes an Undine to wife must be careful not to go on the water with her, or at least must not vex her while there, or she returns to her native element. This notion is elaborated in Fouqué's Undine; see also MELUSINE, SYLPH.