The Merman's Quest by Tamsin Ley

Rubac's mate is dead, and he's soon to follow. His only hope to escape the curse is to find a human female, seduce her, and sacrifice her. Finding and seducing one is the easy part. Sacrificing her may not be so simple.
Searching for a monster...
Madison is determined to document an elusive dolphin hybrid and restore her professional reputation. Instead, she meets a sexy, sleek-tailed beast of another variety who makes her pulse thrum in places it shouldn't. When he pulls himself on board her boat in all his emerald-tailed glory, she jumps at the chance to film him; discovering a mythical creature will secure her the fame she's always dreamed of.
So why is she feeling the need to keep him all to herself?
Content warning: Explicit love scenes and steamy merman secrets. Intended for mature audiences.