I didn't either, but according to WikiHow I don't have to worry about becoming a
midday snack.
Here is one the inspiring tidbits from the article that caught my eye:
Make a sacrifice. As a last-ditch effort, you can try to create a diversion by releasing an
animal carcass or a substantial quantity of raw meat downstream from your desired
crossing point. Keep in mind, however, that the piranhas can indeed strip the animal
to the bones in a matter of minutes or even seconds, so you'll want to cross very
quickly before the fish catch wind of you.
Hey folks, come on down to Amazonia and take a dip in our wonderful waters.
We're dying to have you drop by for lunch.