Thousands of Argentines came here to the Parana River in Rosario on Christmas Day to cool off in a heat wave.
But the holiday mood soon turned to horror when around 70 bathers were attacked by a carniverous fish, related to the piranha.
One of the bathers said some children lost entire digits.
(SOUNDBITE) (Spanish) SERGIO NANI, ARGENTINE WHO WAS ON THE BEACH AND HELPED PEOPLE BITTEN BY FISH, SAYING:
"At around 11:15 in the morning, the first cases of the biting fish came in - I had the first 15 cases, which were in this area. There were injuries of around two and a half, three and a half centimetres with bites that went rather deep. And later they happened in other areas throughout the beach. In total, there were between 50 and 60 cases and there was one amputation."
Officials blamed the attack on the palometa fish, they said the event was "exceptional".