The Opal Cavern

Curl says she' d rather die than spend the rest of her life trapped under Wasso Lake.
What if her wish is coming true?
Nineteen-years-old and still longing to see new things, Curl plans an exploration trip with Lynn' s sons, Mindik and Chera. Their goal is to find Tarth' s legendary Opal Cavern.
Lacht has recurrent, heavy feelings that her Wassandra friend shouldn' t go, but nobody listens and the team leaves.
Then Wave learns something from an old Wassandra diary that can mean life or death for Curl. A rescue team rushes off but they don' t know how long it will take to find her.
They do know that if they don' t find her soon, time will run out before they can get her back.