India, Oct. 17 -- I get my first glimpse of the mighty Amazon from the air as my flight from Lima descends into Puerto Maldonado. The river twists and turns like a brown snake cutting its way through the thick rainforest. A bumpy hour-long drive from the airport brings me to the Tambopata tributary of the Amazon. Once my luggage is loaded into the motorboat, I hop in and don a life jacket.

"Don't put your hand in the water-there are piranhas and anacondas in there," says my guide Victor; I don't need to be told twice.

Over the 45-minute boat ride, we spot many animals, including a bunch of turtles sunbathing on a log and a caiman (a semi-aquatic reptile related to the alligator) slithering on the muddy riverbank. But the highlight is se...