“Just because they’re not venomous doesn’t mean they’re not dangerous....”

Enormous snakes...hungry caimans...frenzied piranhas...and a barefoot biologist! Jesús Rivas takes off his shoes to study giant anacondas in the swampy heart of Venezuela. He’s searching for the slippery skin of the world's largest snake.

Anacondas may be as long as 30 feet and weigh hundreds of pounds - and their weapon is sheer strength, not poison. Powerful coils literally squeeze the life out of prey, including even the Capybara, the largest rodent in the world.

National Geographic cameras capture astounding underwater footage of the anaconda hunting, and document an amazing breeding ball of slithering serpents. Witness the incredible, larger-than-life creatures that inhabit the Land Of Anaconda.

Join barefoot scientist Jesús Rivas in the murky marshes of Venezuela on his quest to understand these huge, fearsome reptiles.

Up to 30 feet long, weighing many times more than the scientists studying them, anacondas are difficult subjects at best, but the National Geographic team captures brilliant footage of them swimming, resting, mating, and hunting prey.

Watch the struggle between a large female and a capybara (the world’s largest rodent) and see that the winner doesn’t always come away from the battle unscathed.

You’ll also see some of the other many hazards of the swamp, such as the anaconda’s venomous cousins and the smaller-but-still-dangerous cousin of the alligator: the caiman.

Produced for National Geographic Channel.