Here’s the good news: piranhas very rarely attack humans unless said humans are already injured or dead. Here’s the bad news, according to Ray Owczarzak, assistant curator of fishes at the National Aquarium in Baltimore: it would only take about 5 minutes for a good-sized school of piranhas to devour an entire man.
Luckily, you won’t encounter piranhas anywhere in the world except South America, where they live only in freshwater, typically in warm, slow-moving rivers and floodplains. If you have your choice of season, pick the wet season (October-March) when piranhas have plenty to eat and won’t be feeling quite as bitey. And it goes without saying, if you see piranhas actively feeding in the water you’re about to cross, choose a different spot unless you’re the sort of person that enjoys sticking their hand into an active blender.