Rex is racing to master the secrets of time and space, in order to defeat the Mantoid menace. He is shocked to learn there is only one way to wipe out the enemy. In order to save the Earth, he must travel to the end of time and exterminate the dark energy that gives the Mantoids their power. But as dark energy is the glue that holds everything together, how can he do it without destroying the universe itself?

Andee is held captive deep in a cave in a marine canyon. Covered in barnacles and tortured by Zadora’s evil goblin sharks as he hangs from the walls, Andee even forgets his own name. Andee’s only hope is a little rockfish that tries to raise his spirits and keep his mind alive. 

Zadora’s magic has become more powerful than anyone could have ever imagined. She plans to flood the world’s cities, engulfing them in tsunamis hundreds of feet high. Only the young Aquanauts, Andee and Indee, dare to stop her in what will be the greatest battle of their lives.