Piranha is one of those movies that sucks me in every time I run across it. Lots of human feeding frenzies going on, one even (surprisingly) at a girl scoutish campsite. In particular, one underwater scene of a camp counselor getting munched was pretty intense. It seemed like everyone you knew would get eaten did not, and everyone you think will live gets chewed. When you notice John Sayles wrote the script, and Joe Dante directed, you realize why it has held up. The "vvdvdvdvvvd" sound when the piranhas attack will crack you up. Very graphic for its time.
