Backahast
Although Backahast is not technically a mermaid, it is a watery creature.
Backahast belongs to Scandinavian legend and is portrayed as a water horse which lives in rivers and lakes.
Backahast usually disguises itself as a floating log or overturned boat so that it can lure unsuspecting people into its lair. Those tempted by the Backahast are pulled under the water and eaten.