Chernava.
Chernava is Morskoy Tsar's (Sea Tsar) daughter, spirit and personification of the river of the same name in Slavic mythology.
Description[]
Chernava appears as one of the 900 mermaids. Her head and upper body are human, while the lower body is a fish's tail. She is described as small, scrawny and young girl.
Overview[]
When Morskoy Tsar offered Sadko a new bride, Sadko took Chernava and lay down beside her. On their wedding night he did not touch her. When Sadko was asleep, Chernava had transformed into a river, helping him to get into the human world. Sadko woke up on the shore of the river Chernava and rejoined his first wife.