After tragically losing his wife while protecting a monitoring buoy, Zhang Yong falls into despair and quits the marine monitoring team, resorting to fishing to support his daughter. Years later, a typhoon brings him back into contact with his old station chief, and together, they uncover a case of marine pollution. Led by the chief, a group ventures into the mysterious Sea Snake Island to uncover the truth behind the pollution—only to find that the island is fraught with dangers far deadlier than giant serpents: human treachery. Defying life-threatening perils, the group ultimately safeguards the marine habitat’s peace. Through this mission, Zhang Yong finally lets go of his past, emerges from his grief, and resumes his duty as a guardian of the sea.