In the movie, a research team led by Sophia and her husband Chris travels to the North Pacific to study the effects of pollution on marine life. They track a shark named Lilith, which has grown significantly in size over the past few months. When Chris and three other divers investigate a sperm whale carcass, Lilith and a swarm of other sharks appear, clearly frightened by an unknown threat. Despite Chris's urging to leave, Sophia insists on obtaining a sample from Lilith. Chris reluctantly wounds the shark, provoking a violent attack that kills the divers. Sophia, hearing their screams, rushes to help with a harpoon but encounters her husband's severed arm and is soon attacked by Lilith. The shark becomes entangled in a fishing net, dragging Sophia into the depths with it.