Four friends, sisters Amber, and Sophie Steele, Amber's boyfriend Jenner Branton, and their friend Bridgette arrive at Red Plum Island on vacation. However, they soon discover several other people crowding around a dead shark on the beach. The shark is suddenly revived, and eats Jenner, and the town sheriff before heading out into the water. Amber manages to contact a man who claims to work for the military, and she, and Sophie meet the man, revealed to be named Maxwell Cage. Amber, Cage, and Sophie return to find a shark attacking swimmers, with Bridgette, and the island's tourism manager Lester warning them. A shark leaps out of the water, and Cage shoots it, although the flaming shark lands on Bridgette, killing her.Amber, Cage, Sophie, and Lester find shelter, and it is soon revealed that Cage is part of a government program in which a shark's DNA was spliced with zombie DNA. Amber manages to contact her parents, although they are helpless to do anything as a result of an impending storm that will hit the island. Later, a zombie enters, although Cage manages to kill it. The group then realizes that whoever the sharks bite turn into zombies. While Lester organizes a group of locals to kill the sharks, Cage contacts his employer Dr. Diane Palmer, who is also the head of the experiments. Palmer tells him that she needs a zombie shark to be delivered to her alive so she can discover the cure.As Lester, and the locals begin killing many of the zombie sharks on the beach, Amber, Cage, and Sophie find a zombie shark, and begin carrying it to the facility where Cage works. They eventually arrive, although when Palmer studies it, she discovers that the cure will only work for those who are close to turning, and will not work on those that have already been infected. The group then decides to kill the remaining sharks by luring them to the facility, and blowing it up. As the sharks begin to approach the facility, Palmer is bitten by the shark the group brought in, and decides to stay behind. As the facility explodes, Amber, and Cage reach the beach, although Sophie is forced to jump into the water to avoid the explosion, and she's eaten by a remaining shark. Lester soon returns, and Amber kills the shark. She then cuts it open, and pulls out Sophie, although she's already infected. Amber reluctantly kills Sophie, and she, Cage, and Lester begin walking to safety.