In Over Her Head

When Erica Peck, one terrified-of-the-ocean marina owner, finds herself at the bottom of the sea conversing with a Mer man named Reel, she thinks she's died and gone to her own version of Hell. When the Oceanic Council demands she and Reel retrieve a lost cache of diamonds from the resident sea monster in return for their lives, she knows she's died and gone to Hell.

When they escape the monster and end up on a deserted island, she amends her opinion – she's died and gone to Heaven.

But when Reel sacrifices himself to allow her to return to her world, she realizes that, Heaven or Hell, with Reel, she's In Over Her Head.