The film tells that Zihao lives in a seaside town and returns to Hong Kong, and lives by the sea to eat. One day, he met the mysterious girl Xiaoyi and began to take care of Xiaoyi's life. The crew of the ocean ship where Zihao's father was located disappeared. After experiencing the pain of bereavement, Zihao came out of the haze under the care of Xiaoyi, and the two were together. But the good times did not last long. A mysterious middle-aged man named Lao Jin came to Hong Kong and revealed the true identity of Xiaoyi-Xiaoyi turned out to be a mermaid! Can Zihao accept Xiaoyi's identity, and can Xiaoyi keep the race secret?