Factual error: When they drain the pool at the abandoned army station, Paul tastes the water and claims the water is salty. Piranha are freshwater fish and would not survive in salt water. (00:19:30)
Piranha (1978)
1 factual error
Directed by: Joe Dante
Starring: Kevin McCarthy, Bradford Dillman, Keenan Wynn, Heather Menzies-Urich
Revealing mistake: At the beginning when the teens break into the waste water plant and start swimming, the boy gets attacked then killed by the unseen piranha, and a large blood pool spills out into the water. The girl is but 3 feet away, but somehow doesn't' see the blood as she calls out his name and scolds him for not responding.
Maggie McKeown: That guard is still out there.
Paul Grogan: Fine, I need you to distract him.
Maggie McKeown: What for?
Paul Grogan: So I can get away.
Maggie McKeown: So you can get away? What about me?
Paul Grogan: Well suit yourself. Just come onto him, tell him what an admirer you are of Army or something like that.
Maggie McKeown: What if he's gay?
Paul Grogan: Then I'll go and distract him.
Trivia: Dick Miller plays the Mayor Buck Gardner, who serves much the same plot purpose as the Mayor Larry Vaughn in the first two JAWS films, in that he insists on keeping the beaches open and dismisses all danger signs. Dick Miller would go on to appear in every single movie ever directed by Joe Dante, right up until Miller's death in 2019.