Kevin J. Anderson & Rebecca Moesta 
Ocean Realm [EPUB ebook] 

The New York Times–bestselling co-authors of Island Realm continue their YA fantasy adventure as Gwen and Vic face their magical enemies underwater. Fourteen-year-old cousins Gwen and Vic are still celebrating their victory in the battle with the merlons when they learn that Vic’s father has finally made it through the crystal doors to the magical island of Elantya. However, their victory is short-lived when they and their friends are kidnapped by their enemies. Taken deep beneath the sea, they soon learn of a scheme that could bring Elantya to ruins. Now they must escape their underwater captivity in time to save the island from destruction?