Nickar

Nickar is a demon or spirit in the Dictionnaire Infernal. In Scandinavian, Teutonic and Saxon mythology, Nickar are malevolent water spirits who drown people, torment fisherman, tip over boats and throw them to the tops of shore-side trees. According to mythology, Nickars or Hnickars patrol the waters of Scandinavian fjords, where they cause tempests, hurricanes, hailstorms and blizzards. They have fish-like tails and often sit by the water combing each other's long green or blonde hair with seaweed, playing a harp or singing. Like the Sirens, they drag to the bottom of the sea anyone who ventures too close.