In Actun Tunichil Muknal, which is the most spectacular of the Maya caves that Dr. Awe's working in, there's this beautiful, beautiful entrance pool full of fish, and I wanted to take a picture of him swimming through it.

I think it's the only time I've ever actually had hypothermia in the tropics, because the water's about 70 degrees [Fahrenheit/21 degrees Celsius] and we spent so long in there, swimming back and forth and taking pictures of him. ...

I think at one point he had finally panicked and he was ready to kill me anyway. He was about to put his arms around my neck and say, "You've got to let me out of this pool!"

The sacrifices [in these caves] really began to pick up at the end of the Classic period, right when the Maya world was breaking down. ... They were doing very extreme things ... sacrificing children just to try to make the rain come so they could eat.

—Photographer Stephen Alvarez