The thrilling third installment of the underwater fantasy adventure series-perfect for fans of Keeper of the Lost Cities and Percy Jackson.

Thirteen-year-old Alessia knows she can't trust the dangerous magic swirling inside her-but when a legendary gemstone lands in her scheming mother's hands, she must act fast to save the underwater realm of Atlantis.

Her mother's plan? Fulfill a dark prophecy and rule both land and sea...

Only by solving a cryptic, centuries-old riddle can Alessia stop her. For that, Alessia and her friends will have to race through Bermuda Triangle shipwrecks and underwater volcanoes, dodge devious mermaids, outwit coral pixies, and face rampaging sea monsters.

But Alessia is fighting another battle-against the voice in her head tempting her to claim the prophecy's power for herself...

Grab your wetsuit and dive in-because under the sea, a secret that will change everything is waiting to surface...