+1
After watching the movie, it was obvious that whoever wrote the screenplay had read Stone's (and Barbara's!) book but I think it's safe to say that it was a blend of two well-known expeditions.
Also, it's worth noting that the book in question(Beyond the Deep) is based on a Huautla expedition. It has nothing to do with Cheve or Charco (or J2 for that matter), which seems to really confuse people. The caves are close to each other, but entirely different beasts.
-Jon