Rusalka

In Slavic folklore, the rusalka is a female entity, often malicious toward mankind and frequently associated with water. It has counterparts in other parts of Europe, such as the French Melusine and the Germanic Nixie. Folklorists have proposed a variety of origins for the entity, including that they may originally stem from Slavic paganism, where they may have been seen as benevolent spirits. Rus... (Wikipedia)