Chloe has moved to Zanzibar because her mom will be working on the island as a marine biologist. As soon as she arrives, she starts exploring the underwater world together with her new classmate Amo. While swimming in the ocean, they meet a dudgong named Nya. She shows them her home - the seagrass meadow made up of green, thick leaves as fas as the eye can see. In between they can spot all kinds of colorful animals. Chloe and Amo are immediately fascinated by this underwater wonderland.
However, when they return a few weeks later to the beach after a particularly hot summer, the seagrass meadow has disappeared along with their friend Nya. A sandy desert is all that is left. What happened and what can they do? Chloe and Amo set out to bring back their underwater forest.