The mermaid that appeared in China and the missing diamond ocean star. The mermaid traveled to the present and fell in love with humans. Facing the destruction of the protected sea by humans, the underwater world is in danger. Human scientists want to catch the mermaid and start exploring the resources of the underwater world. The mermaid princess should choose to protect her love or defend the seabed and fight against humans. Will the tragedy of the mermaid princess's mother's love happen again to her daughter? . . .