Two hikers find an old pool in a fenced off compound in the woods and decide to go skinny dipping, but something in the pool devours them.  Later, a young and ambitious but completely inexperienced skip tracer, Maggie (Heather Menzies, Endangered Species) sets out to find the hikers.  Guided by local alcoholic and unemployed lay about Paul Grogan (Bradford Dillman, The Swarm), Maggie finds the nearly abandoned government research station where the hikers disappeared.  They find a seemingly crazed scientist, Dr.  Hoak (Kevin McCarthy, Invasion of the Body Snatchers), whose evasiveness, plus the fact that he’s hidden the hikers’ gear, convinces Maggie and Grogan that he’s killed the hikers and thrown their bodies in the pool.  Hoak attempts to stop them from emptying the pool, but he is knocked unconscious and the pool drains into the river.

When Hoak comes to, he beings raving and warning them that they’ve released the results of an Army biological warfare program-piranha that can live anywhere-into the river.  Hoak wrecks Maggie’s jeep, forcing the group to take a raft downstream.  Along the way they discover that Hoak is not mad, and that engineered piranha are loose-and incredibly dangerous.  The pair meet Hoak’s fellow scientist Dr. Mengers (Barbara Steele, The Ghost) and Colonel Waxman (Bruce Gordon), who assure them that their poison will kill the fish-but promptly put them in jail when they try to warn the people downstream-including a camp where Grogan’s daughter is staying and a resort run by huckster Buck Gardner (Dick Miller, A Bucket of Blood), who just happens to be in bed with Waxman.  Can Maggie and Paul escape prison in time to warn the people downstream and stop the killer fish?

Back in the late 1970s, greedy filmmakers tried almost every conceivable way to rip-off the phenomenally successful Jaws.  They brought audiences killer sea creatures of every ilk (octopuses, killer whales, every variety of shark, sea monsters, crocodiles, and alligators), bears (including at least one mutant bear), giant apes, a giant white buffalo, even killer cars.  Piranha is one of the many films made in this explosion of cash-ins.  A few things set it apart from other films of its ilk.  One is that it playfully recalls earlier films, both recent (Maggie appears playing a Jaws video game) and older (the casting of cult actors like Steele and McCarthy, not to mention the little stop motion beastie that lives in McCarthy’s lab).  In many ways Piranha is a satirical black comedy, with a small but very funny role as a strict camp counselor for Paul Bartel (Rock and Roll High School) in addition Dick Miller’s Buck Gardner, Steele’s Dr. Mengers and Gordon’s Colonel Waxmen sending up business, scientists, and the military.  Of course, Dillman and Menzies are hardly ultra competent characters, but it is nice that by and large the victims are nice people (Belinda Balaski’s camp counselor for example) rather than caricatures that we want to see die.  Hell, Bartel’s tyrannical counselor even gets a mea culpa moment.  True, there are missteps such as Keenan Wynn’s (The White Buffalo) old fart character, but touches like using pollution as a weapon against the fish keeps it fresh.

Director Joe Dante (Explorers) and screenwriter John Sayles (Battle Beyond the Stars) were fresh young talent, eager to make the best of the chance that producer Roger Corman (The Beast From Haunted Cave) was giving them, and it shows.  Not all of the comedy works, and the suspense and horror side of things is okay at best, the special effects are down right silly at times, but it doesn’t matter, as it is a fun film (obviously made by filmmakers who knew and loved the genre) with a game cast.  Piranha was rightfully a cult hit.  None of the film’s sequels or remakes have managed to create the same mix of comedy, homage and cast that makes the original film refreshing and fun.