Kai Merlin is heir to her mother's throne in Atlantis, and she takes her duties seriously, but lately her mind has been on her fiancée Vivien Palmer. After a chance encounter when they were children, meeting again and falling in love proved to be fate, but melding their worlds as they plan their wedding isn't going to be easy.

Vivien has spent her life searching for the secrets she'd always known were hidden beneath the waves, but nothing prepared her for what Kai and her people had successfully kept hidden for eons. She finally has a sense of belonging, but unseen enemies will stop at nothing to conquer and destroy their world—including everything and everyone she holds dear.

Below turbulent waves, Kai and Vivien must fight for what is right as life and love hang in the balance.