Transcript for Piranhas Attack Dozens of Swimmers on Argentine Beach
To a close call for families swimming, stunned when they were surrounded by piranhas. They got out but not unscathed, abc's matt gutman with the dramatic pictures tonight. Reporter: In feeding frenzies like this one captured by animal planet's "river monsters," piranha can devour everything, even bone. And so it was on this argentine beach on christmas day, packed not just with bathers but a pack of piranha, attacking dozens of swimmers right on the shores of argentina's second largest city of rosario. Chomping into these men, and biting off one girl's fingers. Eating into this boy's ankle. One of the worst attacks in memory. Officials say the beach was packed with thousands of bathers because of the soaring heat, over 100 degrees. The heat wave also being blamed for drawing in the piranha, 9 the fish have long fed into big popular nightmares. Fodder for hollywood flicks like "piranha 3-d" watch this national geographic video of an egret falling into piranha infested waters, the water seems to boil as they devour the bird, leaving only feathers. In fact, pound for pound, piranha's bite is more powerful than a great white shark, and three times stronger than a gator's. And they can smell blood from up to two miles away. But as we learned when we swam with anacondas in the amazon last year -- this is insane. Reporter: And tracked down wag jaguars -- in streams teaming with piranha's the critters most often leave human's alone. Which is what the argentine swimmers were perhaps banking on, when they went right back in the water today. Matt gutman, abc news, miami.
This transcript has been automatically generated and may not be 100% accurate.