Rusalka are the Slavic variation of the siren myth. During the daytime, these half-fish, half-women dwell at the bottom of lakes and rivers. By night, they emerge and seduce men, leading them into the water to drown. According to legend, the Rusalka are the spirits of young women who died untimely deaths, particularly unwed mothers, and thus pine for the affection of men and young children. Most aren’t aware they’re dead, and are not maliciously motivated.
Some also manifest as children who were aborted for being conceived out of wedlock, or infants who died before baptisms. If the spirit is avenged, or baptized as a child, it will return to a place of rest.