After his family falls into decline, Lin Yu goes to the tidal flats of Dong'ao Village to gather seafood. By chance, he discovers the Fish King's Command Token, gaining the ability to command all marine creatures within a one-kilometer radius. Starting with swimming crabs, he builds his fortune alongside his childhood friend Zhou Xiaopang, catching valuable seafood such as groupers, mouse groupers, and large yellow croakers. He buys back his family's old home, restores their fortunes, and gets to know Shen Zhixia, the owner of Guanhai Yipin. When Lu Zhenting plots to seize control of the sea for profit and destroy the Sea Eye, Lin Yu follows Master Jiao's guidance and discovers his true identity as a guardian of the sea. Joining forces with local fishermen, he establishes a cooperative and ultimately defeats his rival, protects the vitality of the coastal waters, finds love, and builds Fish King Harbor.