This panic-inducing thriller depicts an unprecedented tsunami hitting Haeundae, a popular beach in Busan, South Korea. Fisherman Man-sik (Seol Kyung-gu), still traumatized by the loss of a colleague in a previous tsunami, refuses to believe the new tsunami threat predicted by geologist Kim Hwi (Park Joon-hoon). Meanwhile, his ex-wife, Yeon-hee (Ha Ji-won), who now runs a restaurant catering to tourists, lives her daily life with her teenage daughter. Soon, just as Kim Hwi warned, an unimaginable tsunami strikes Busan. In an instant, people's lives are taken away, and they are forced to fight desperately for survival. Separated from family and friends, Man-sik and Yeon-hee also embark on a desperate survival mission. The film portrays the destructive power of the tsunami, the human bonds that emerge, and the extreme choices they must make, illuminating both the horror of disaster and the strength of humanity.