What a classic drive-in schlockfest. From the Roger Corman stable, Piranha could have been just another cheap Jaws ripoff, à la The Last Shark. But Corman hired filmmakers with some genuine talent to write and direct. He was way too tight to give them a budget, but their skills allowed them to weave some shitty gold.
John Sayles wrote the screenplay and Joe Dante directed. This was very early in both their careers, and they have since gone on to greater things. But I wouldn’t call this a humble beginning. By 1978, when this flick was released, Corman had been in business for decades. The flicks he produces are not humble — they are just cheap.
Piranha stars Bradford Dillman as Paul Grogan, a gruff individualistic drunk who has pulled back from civilization, choosing to spend his days in a cabin in rural Texas. Think of a slightly sloshed Charlton Heston and one will have a very good picture of Dillman’s performance. He is joined by Heather Menzies-Urich as Maggie McKeown, the most unlikely skip tracer in history. No Jack Walsh or Duane Chapman this.
Maggie is up in Grogan country searching for a pair of hikers who went missing. She doesn’t know what happened to them, but viewers do, thanks to an introductory scene. The two youths are dead, chewed to pieces by mutant piranhas. So, how did the hikers come across piranha in Texas? While on their hike, they came across an abandoned Army research station. There, a secret weapons program had been breeding a species of piranha capable of surviving in cold water. The idea was to 
release the piranha in the rivers and streams of North Vietnam like a plague. But, we went and lost the war before the experiments were complete.
Viewers learn all of this through helpful exposition by Dr. Robert Hoak (Kevin McCarthy). He was a scientist at the facility, and stuck around to carry on the experiments after the Army shut everything down.
By this point in the film, the piranha are only a threat to anyone unfortunate enough to go swimming in their pen. That wouldn’t make for much of an exciting movie, so mistakes are made and the piranha are released into a local river. Now everyone downstream is in danger.
The first victim out in the wild is Keenan Wynn, who showed up for a day of shooting and a paycheck. His death set the tone for the rest of the film, even more so than the deaths of the poor hikers. He’s enjoying life, fishing off the end of his small dock, his dog at his side. But, he made the mistake of dangling his feet in the water. The piranha set to, but rather than lifting his feet from the water, Keenan sits there and screams while the fish gnaw his legs to the bone. That’s some prime shitty.
But, it’s also intentional. Piranha is not a spoof, nor is it a straight comedy. It’s not a black comedy, either. What it does have is occasional absurdity and scattered moments of levity. It keeps things lighthearted, which works well. It has to. After all, this is a flick about little killer fish.
After the piranha make their way down the river, all hell breaks loose, and the Army gets involved again. Barbara Steele joins the cast at this point, playing another scientist involved in the original project, Dr. Mengers. Her performance was the most precious of the bunch. Every line was delivered with a wink and a nod, like she was playing ham in a comedy sketch.
That’s enough for plot. What about blood? There is plenty of that. This flick isn’t all that gory for a horror flick of the era, but there is plenty of the red stuff. It starts with Keenan’s mangled feet, and moves to a mass feeding frenzy at a beach. Legs get chewed. Torsos get chewed. Faces get chewed. And the river flows red. Glorious.
And totally silly. A deadly school of piranha invade a Texas river? Yeah, okay. Piranha is stupid, cheap schlock, and it’s fun. As s shitty movie watch, it’s better than most, landing at #66 in the Index between Escape from the Bronx and Chopping Mall.