A popular vacation spot on the south coast of Korea, Haeundae draws visitors from all over the country. During its peak season, more than a million vacationers pack onto its narrow one-mile strip of sand. Marine geologist Kim discovers the Korean East Sea is showing signs of activity similar to that of the Indian Ocean Tsunami in 2004. Arriving in Haeundae to warn the authorities, he runs into his ex-wife who is accompanied by their 7-year-old daughter whom he has never met, consequently stirring up various emotions. In the meantime, a giant tidal wave is created and headed straight for Haeundae where the vacationers enjoy a summer day, unknowing of the 500 MPH destructive force of nature headed their direction.