Eight-year-old Xu Xiaoman has a secret: she can understand sea creatures when they talk. On the verge of bankruptcy, an old aquarium spends 50,000 yuan to bring back Dafu, a supposedly crazy sea lion. Xu Xiaoman discovers that he's actually just afraid of a red-clawed crab and cures his emotional troubles. A dolphin that can do arithmetic, a seal that's afraid of people, and otters that fight over food are all persuaded by Xu Xiaoman. With her help, the rundown aquarium makes a spectacular comeback and is packed with visitors every day.