Franklin, owner of the biochemical pharmaceutical factory (Samuel L. Jackson) provides substantial funding for Dr. Susan McArester (Saffron Burrows) to research anti-Alzheimer's drugs. Susan and her research team extracted proteins from shark brains and injected them into necrotic human brain cells at a well-equipped undersea research center. In order to extract more shark brain proteins, Susan also increased the brain volume of the sharks. This move made the sharks, which were originally test subjects, stronger and smarter. Shark expert Carter (Thomas Jane) discovered the abnormality of the sharks while spending time with them and warned Susan, but Susan ignored it. Finally, in the last test, those ferocious sharks who had once become human guinea pigs retaliated against humans...