Ceasg

The Ceasg is a form of mermaid-like creature from Scottish myth. They’re known to live in lakes and on the coast. They have the upper body of beautiful women with the lower body of salmon, though they turn fully into human women if they fall in love with a human. Any children they have will have a strong connection to the sea. If unloved, they express their anger by leading fishermen to drown. They have been known to overturn boats, punch holes in boat hulls, and use fishing nets to pull humans into the ocean to die, and can be easily offended. 

Citations:

Maberry, Jonathan. Vampire Universe: The Dark World of Supernatural Beings That Haunt Us, Hunt Us, and Hunger for Us. United States, Kensington Publishing Corporation, 2006.