Located on the southeast tip of the Korean peninsula is the international city of Busan. A popular vacation spot on the East Sea coast, Haeundae draws one million visitors to its beaches every year. Man-sik, a native of Haeundae, lost a co-worker to a tsunami on a deep-sea fishing trip four years ago. He has never returned to sea ever since. He now leads a simple life running a small seafood restaurant and is preparing to propose to his longtime girlfriend, Yeon-hee. Man-sik's brother Hyung-sik works for the coast guard. One day, he rescues a female college student from Seoul who promptly, comes on to him aggressively. While these everyday domestic affairs unfold, geologist Kim Hwi, an expert on tsunami research, discovers the East Sea is showing signs of activity similar to the Indian Ocean at the time of the 2004 tsunami. Despite his warnings, the Disaster Prevention Agency affirms that Korea is in no harm of being hit. Then, he discovers that a mega-tsunami is headed straight for the Korean peninsula. With only minutes to spare, vacationers and citizens of Busan are enjoying a peaceful, hot summer day, and a mega-tsunami is headed straight for Haeundae at 500 miles per hour.