Scientists Susan McCallister (Saffron Burrows) and Jim Whitlock (Stellan Skarsgård) are conducting research on regenerating brain tissue in sharks, hoping to find a cure for Alzheimer's disease. But when their funding is threatened, the pair decides to take a dangerous shortcut. Through DNA modification, they breed larger sharks with larger brains -- and near-human intelligence. Soon, the sharks grow resentful of their captivity.