"Who am I?" wonders Shark Baby. When his "mermaid's purse" egg case is torn loose in a storm, he finds himself on a journey through different ocean habitats: kelp forests, coral reefs, and seagrass meadows. He learns what kind of shark he isn't but not what kind he is. He needs to find the "mermaid" to learn where he belongs, but the ocean is big and full of dangers. Will he find out who he is - and what he can do - in time?