Transcript for Book to reveal new details about Thai boys' harrowing rescue from cave

Finally tonight here, it was the rescue the world held its breath for. Those boys in the cave. And tonight, what we never knew about the U.S. Air force team who suddenly had to plan their own way out. Here's ABC's Matt Gutman. Reporter: The U.S. Air force team that planned and organized that daring rescue forced to make its own harrowing escape after that Thai cave flooded. Two American airmen, the very last people out. Going in, they feared that many of the boys would die during the rescue. We either have a shot where we could get some of them out, or we leave them in there and there's a very, very high chance that none of them survive. Reporter: 12 soccer players and their coach became trapped in that cave this summer during a flash flood. For ten days, no one knew if they were alive or dead. How many of you? 13. Brilliant. Reporter: We've learned in reporting the book "The boys in the cave," that two of the boys barely made it out. One was hypothermic, another stopped breathing. We visited a nearby cave to get a sense of the conditions rescuers faced. Imagine going through that with 60, 70 pounds of gear, tanks. And tonight, the first images of the cave since the moment the cave flooded at the very end of the rescue. Those air tanks and water bottles still there. Those tanks still in place. Our thanks to Matt. And his new book, "The boys in the cave" and the rescuers and their fears that that rescue wouldn't be a success. Remarkable reporting, Matt.

This transcript has been automatically generated and may not be 100% accurate.