Killer Fish is a 1978 Italian-French-Brazilian horror movie directed by Antonio Margheriti and written by Michael Rogers. It starred Lee Majors and Karen Black.
The plot revolves around a criminal mastermind who steals priceless emeralds and decides to hide the jewels at the bottom of a reservoir he’s secretly stocked with savage deadly piranha.
Retrieving the gems turns to be a caper in itself since the group is now torn by suspicion and jealousy.
Several gang members try to recover the loot on their own, only to become screaming victims of the insatiable horde of killer fish. The treasure is down there just waiting to be brought up.
To get them, everyone must face the inescapable terror of thousands of man-eating creatures.