I had too much fun laughing at this to vote it lower than a 5.
Piranhas are already pretty fearsome creatures. So naturally, some scientists genetically mutate them. Things go wrong; the creatures escape into a Venezuelan river, and start to "grow exponentially." So a big guy on steroids named Fitch is sent to aid Venezuelan soldiers to fight the menace. They look like Castro impersonators, and end up chasing him around, for whatever reason.
When the Sec. of State looks like a Brady and is named Grady, you know the "Asylum" movie makers are just "winking at the audience." The action-film meets sci-fi motif is played with over-the-top gusto: look for piranha jumping high into the air and slamming their victims down like a sledgehammer. I didn't know they could do that. Even mutated ones. Steroid Fitch kick-boxes an entire school of piranha senseless in a great Jackie Chan moment. The super-sized creatures crash themselves into Key West hotels. Battleships get turned into Fish Filet sandwiches. The TV news reporter doing play-by-play of a piranha attack, the bit about tail fins, Col. Valdez inexplicably showing up in Florida; hilarious.
Most of the time it makes absolutely no sense what's going on, with absurd scientific plot holes everywhere. There's no intent for this to be taken seriously; and taken at face value it's classic B movie silliness.
