Off the coast of an isolated island, fisherman Hunter Shaw, his assistant Ray McCray, and Ray's niece Jada are attacked on their boat by a zombie that bites Jada before Hunter knocks it overboard. Jada is taken to a hospital with Ray, where she is tended to by doctor Kenzie Wright. Wright's daughter Samantha, and her friend Taani Akoni are at a local restaurant where they meet the members of a local band, Dag, and Ivan. Taani's sheriff father Kameo takes a boat onto the sea with Hunter to investigate the location of the incident. They soon witness hundreds of zombies swimming in the water before a tidal wave takes them, and the zombies onto land.At the hospital, Jada turns into a zombie, forcing Ray, and Kenzie to hide. Samantha's group is attacked by zombies, and Ivan is killed, and Taani is separated from the others. Hunter, and Akoni reach Akoni's car, where they find couple Blaine, and Connie hiding inside. The group drives to the police station, although Blaine sacrifices Connie to the zombies as they run inside. Blaine attempts to force officer Pok to drop his weapon, and ends up shooting him to death before Hunter knocks him unconscious, and Akoni handcuffs him to a bench. As another tidal wave approaches, the two drive off. After they leave, Blaine awakens, and frees himself, only to be killed by the infected Connie.Taani escapes to a mansion owned by Marty Driscoll as her father calls her, and she confirms her location. Hunter, and Akoni then rescue Samantha just as Dag is killed by a zombie, and the group drives to the hospital, where they reunite with Ray, and Kenzie, and Hunter discovers the zombies can be killed by electrocution. The group drives to Driscoll's mansion, and reunites with Taani, although zombies invade the property, and the survivors are forced to flee to a nearby cave. When it is discovered Akoni has been bitten, he reveals that he was assigned to cover for a company that was attempting to create a biological weapon under the guise of a de-aging serum; the zombies are the result of the weapon being released. As Akoni transforms, and other zombies arrive, the group is forced outside, with Akoni managing to set off a grenade, and kill himself, and several zombies before he turns.The group resolves to end the threat by luring all of the zombies into a series of nearby tide pools, and electrocuting them while also blowing up the weapon material at the bottom of the ocean. Hunter, Kenzie, and Samantha go to the tide pools as Ray, Taani, and Driscoll head out to sea, although Driscoll is devoured by the zombies as he attempts to place the bombs. While Hunter, Kenzie, and Samantha kill the remaining zombies, Ray has Taani swim for shore before blowing up the boat, and himself, as well as the material, causing a third wave that breaches land, although Hunter, Kenzie, and Samantha survive. They then rescue Taani from the water, and the four survivors agree to stick together as they watch the sun set.