The World's My Oyster Book Three: Tsunami
25 parts Complete Summer's almost over, and things are changing for the mermaids. Rikki, Cleo, and Annabeth have lost two of their numbers, and with newfound relationships (and a baby), plus college, the expectations have never been higher.
But when new mermaid Bella arrives claiming to know all about demigods, and the moonpool starts attacking them, things get even more complicated. And then teens start showing up--teens who claim to be from a future where they fail to save the world.
Can the demigods and mermaids work together one last time to save those they love? Or will they be swept away?