The film focuses on Haeundae, a tourist resort in Busan, South Korea. A sudden tsunami mercilessly destroyed everyone's happiness.
Wan Zhi (Xue Jingqiu), a native of Haeundae, Busan, South Korea, lives in a quiet place. He has lived on a fishing boat since he was a child and has been working with his most dependent father, Yan Xi. Unexpectedly, in 2004, the most shocking Indonesian tsunami happened. At that time, two people on a fishing boat in the Indian Ocean died because of Wan Zhi's misjudgment, which made Wan Zhi, who had always secretly loved Yan Xi (Ha Ji Won), afraid to confess because of his guilt. Finally, one day, Wan Zhi got up the courage, decided to show his love to Yan Xi, and prepared a romantic proposal. However, Wu Dongchun (Jin Renquan), a middle school classmate in Yan Xi, is not optimistic about this evil couple. Wan Zhi's younger brother Zhi Heng (Li Minji) is a lifeguard at sea. In an action, he met a rich girl, Kim (Jiang Yiyuan). In their communication, they have many misunderstandings.