Located on the southeastern tip of the Korean Peninsula, the Haeundae district of Busan draws one million visitors to its beaches every year. The film follows the stories of many characters who all get caught up in a terrible tsunami in which they must make life-or-death decisions. Five years ago, Man-sik, a Haeundae local, lost Yeon-hee's father due to his mistake in the 2004 Indian Ocean earthquake. Because of this, he could not become involved with Yeon-hee, who runs an unlicensed seafood restaurant, despite her attempts to start a relationship. Dong-choon and Seung-hyun's grandma team up with Seung-hyun and get involved with some illegal activity to earn money, but end up getting caught by the police. Man-sik finally plans to propose to Yeon-hee. Geologist Kim Hwi runs into his divorced wife, Yoo-jin. Although Yoo-jin has a daughter named Ji-min and a new boyfriend Hae-chan, they decide not to tell their daughter that Hwi is her real father. A wealthy college student from Seoul, Hee-mi, accidentally falls into the sea from a yacht. Hyeong-sik, Man-sik's younger brother, is a lifeguard who rescues Hee-mi. Hee-mi becomes angered by the 'violent' rescue and annoys him by following him around and the two begin to fall in love. Hwi notices that the Sea of Japan is displaying similar activity to the Indian Ocean at the time of the 2004 Indian Ocean earthquake. The Disaster Prevention Agency assures him that South Korea is at no risk, but a megatsunami soon forms near Japan and starts to travel towards Haeundae. Hwi realizes that the citizens of Haeundae have only 10 minutes to escape. There is a short earthquake at Haeundae. The sea starts receding from the shore, causing mass hysteria as people realize that a tsunami is coming. Thousands of people run for their lives, but the tsunami reaches Haeundae. Dong-choon, Seung-hyun, his grandma, and other people on the Gwangan Bridge are swept awayby the sea. A powerful electric shock from a telephone pole on a street where Man-sik and Yeon-hee are electrocutes everyone in the water, but the two survive. Dong-choon awakens on the bridge, but when he tries and fails to light a cigarette, and subsequently discards the lighter out of frustration, it falls into petrol leaking from a tanker, causing an explosion that severs the bridge in half. Hyeong-sik jumps down from a rescue helicopter and saves Hee-mi in the sea. When Hyeong-sik and the rest of the group are together on the rope, Hyeong-sik realizes that the rope is about to break and only one can go up to the helicopter. He cuts the rope he is connected to and falls into the violent sea. The elevator Yoo-jin is trapped in floods with water, and she talks in tears to her daughter Ji-min on her phone. Yoo-jin is saved by a worker. On the roof, she meets Ji-min and Hwi. The two help their daughter get on a crowded rescue helicopter. Before the helicopter leaves, Hwi tells his daughter that he is really her father. Yoo-jin and Hwi hug each other before they are killed. After the tsunami, there is a funeral for the thousands of people who were killed. Among the dead is Hyeong-sik and Man-sik's uncle. Dong-choon finds out that his mother died as well and breaks into tears. Many people help reconstruct the city. Man-sik, while cleaning the ruins of Yeon-hee's restaurant, finds the red ribbon which Yeon-hee said was a 'yes' to his proposal. The movie ends with a scene of Haeundae in ruins, but in a hopeful atmosphere.
