Crystal Doors #2: Ocean Realm

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 underwater enemies and taken beneath the sea they soon learn of a scheme that could bring Elantya to ruins. Can they escape in time to save the island from destruction?