As a boy growing up in Peru, Andrés Ruzo recalls his grandfather’s stories about the horrors Spanish conquistadores encountered in the Amazon, including a “boiling river.” Years later, Ruzo, a National Geographic Explorer, journeys into the Amazon to try to find the waterway. For more information on this episode, visit nationalgeographic.com/overheard. Want more? Read Andrés’s book: The Boiling River: Adventure and Discovery in the Amazon. Also explore:  Curious what you can do to help the river’s ecosystem? Go to www.boilingriver.org.  For subscribers:  Read a Q&A with Andrés to learn more about the communities that live around Shanay-Timpishka and the theories scientists explored to understand why the river boils. Learn more about your ad choices. Visit megaphone.fm/adchoices