A Mermaid's Tale (Re-writing)

The death of Kate's parents from when she was six years old has never been able to escape her. They didn't die from an illness, or a car accident but they were murdered. It's not that simple to find their killer because their killer is not human. It lives in the deepest depths of the ocean and Kate, now sixteen years old could find herself falling for her parents killer without even realising it, and falling for someone who isn't even human.