Sac Actun River, Mexico, page 40

AUTHOR'S NOTE Selecting which rivers to include in this book was not a simple task. There are so many rivers on Earth —each one unique and remarkable in its own way— but not enough pages for all of them. It was not a random selection, as I aimed for variety in geography and topic. My guidelines were clear: I would have room for only about 100 rivers from around the world, and each one needed to exemplify something fascinating, surprising or awesome. I hope you enjoy discovering these amazing rivers as much as I did!