The U.S. Navy commissions a group known as "Blue Water" to genetically engineer a half-shark, half-octopus for combat. During a demonstration attacking drug traffickers off of Santa Monica, the beast called Sharktopus escapes the control of its creators and makes its way to Puerto Vallarta. Hunted by Blue Water and a television crew, Sharktopus attacks numerous beach-goers. Sharktopus is eventually defeated by detonating explosives embedded in its brain.
In an interview with Flixist.com, producer Roger Corman said that he may do a sequel to the film. A similarly themed movie, Piranhaconda, was released in 2012. Two official sequels called Sharktopus vs. Pteracuda, which was released on August 2, 2014, and Sharktopus vs. Whalewolf, which premiered on July 19, 2015 during Sharknado Week on the SyFy Channel. Another sequel titled Sharktopus vs. Mermantula, was announced in the credits, and would feature a man/piranha/tarantula hybrid.