The man reveals himself to be Doctor Robert Hoak, lead scientist of a defunct Vietnam War project, Operation: Razorteeth, tasked with engineering a ravenous and prodigious strain of piranha that could endure the cold water of the North Vietnamese rivers and inhibit Viet Cong movement. The project was shut down when the war ended, but some of the mutant specimens survived, and Hoak tended to them to salvage his work. Grogan realizes that if the local dam is opened, the school will have access to the Lost River water park resort, and the nearby summer camp where his daughter Suzie is in attendance. They encounter a capsized canoe with a boy whose father has been killed by the piranha. Hoak rescues the boy, but suffers mortal injuries when the school attacks him; he dies before he can reveal how to kill them. Blood from Hoak's corpse causes the piranha to tear away the raft's lashings, and they barely reach shore. Grogan stops the dam attendant from opening the spillway and calls the military.