Meet Oona. The big sea’s littlest mischief maker.

She and her best friend, Otto, love to search for treasure . . . but often find trouble instead.

Messy trouble.

Tricky trouble.

Even shark-related trouble.

That’s never stopped them before, though!

After all, no proper treasure hunt is without some adventure. But when the grandest treasure yet is stuck in a deep, dark rift, Oona’s not sure if she can dive right in. What might be waiting for her in those unknown waters?