This is Dr. Awe in one of his caves. This is one of the places where he won't bring tourists, because the cave itself is too dangerous. The water's too deep and fast and the sides of the cave are very slippery. It's in this particular place—the first time in, he slipped and fell, almost fell to his death.

[Awe is] heading in upstream, and that's [writer] Dave Roberts in the background. ...

The great thing about David is he doesn't swim. Not only does he not swim, but he's kind of terrified of water. I was just so impressed with him because he got a really good handle on his fear on this trip. ... He started off wearing this puffy orange life vest that—I think he appreciated how ridiculous it made him look.

—Photographer Stephen Alvarez