Piranha mouth open showing teeth
Electra the electric eel at 1939 the World's Fair
bird-eating spider, theraphosa leblondi, ca
Tiger fish (Hydrocyon vittatus) Zambezi River
A frog dangles from the mouth of a crocodile in South Africa.
Snakehead fish
Chelus fimbriatus, or mata mata, turtle
Divers with catfish in the Great Lake at Ostersund in north Sweden
Diving bell spider (Argyroneta aquatica)
Anaconda
Freshwater stingray
Fanged payara fish in Pevas, Peru
Candiru, parasitic catfish
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PiranhaNotorious for their sharp teeth and voracious appetites, piranhas inhabit several of the major river basins in South America. These omnivorous fish are known for their taste for meat, although attacks on human beings are quite rare, despite breathless accounts from early explorers. In a historic visit to Brazil, Theodore Roosevelt famously saw a group of piranhas shredding pieces of a cow carcass in seconds. His dramatic account would color...
Photograph by Martin Shields, Alamy

13 Scariest Freshwater Animals

From the fearsome piranha and vampire fish to the mighty anaconda, the crocodile, and the candiru, these are among the most terrifying reptiles, insects, spiders, and fish.