Dark Shores. Black Depths, #3

In Tales of a Redheaded Sea-Witch, sixteen-year-old Nessa learned she has a destiny she can't walk away from. Now, months later, she knows just what being a Neptunian really means. Her friends have been stolen from her, and her boyfriend has left her to find them, but now Nessa, too, leaves the safety of the island in a desperate attempt to find her friends before the evil pirate, Victor Jimenez, kills them.
Beginning in Northern Ireland, and on the doorstep of a great-aunt she's never met, Nessa begins pursuing the trail of the power hungry Neptunian bent on taking over the world. As the mystery unravels, Nessa finds herself circling the globe with her best friend, Amynta, as they follow one lead after another. Not only does Nessa learn more about the Neptunian world she lives in, but she learns about herself, and the lengths she will go to in order to protect those she loves.