This comical and heartfelt picture book is a winning celebration of invention, creativity, and friendship.

With gorgeous underwater scenes and a crowd-pleasing tale, this is one little mermaid who is here to make a splash!

New York Times bestselling author Kelly DiPucchio and illustrator Raissa Figueroa would like to introduce Oona-the big wide sea's littlest mischief-maker. Oona and her best friend Otto love to search for treasure...and 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?