Piranha (1978)

Maggie has to investigate the mysterious disappearance of teenagers who disappeared under very strange circumstances. During the search, she had to get acquainted with Paul, who leads a hermit lifestyle and suffers from alcoholism. The man was not very friendly at first, then agreed to help the woman, given that his knowledge of this area is very high. Together they manage to find the teenagers' belongings lying around the pool located near a small military building. The hermit decides to dive into the water to find the remains of the missing, but all efforts worsen the already too difficult situation.

A scientist who lived in a military facility discovered by the main characters tells about the tests carried out in this place. The experiment was conducted on piranhas, from which it was planned to breed dangerous killers capable of living in cold and salty waters. When the Vietnam War was stopped, the project was shut down and the fish were poisoned. But not all the individuals died then, some were able to survive and breed, creating a serious threat to society. Now the problem was that dangerous predators had escaped into the reservoir and were attacking people. There may be more victims if piranhas, during the descent of water from the reservoir, penetrate to other water sources.