Here's another stupid hiker story from the book. A helicopter pilot was flying over Havasu Canyon, I believe and noticed a flash flood forming high in the canyon. Knowing that there would be lots of people hiking in the canyon, he decided to ignore regulations and fly down the canyon to warn people. He went from group to group using hand gestures to indicate they should leave the canyon. Most understood him and moved.
He came to a pair of women who were wading in the creek and when he signalled, they just waved back, thinking he was being just being friendly. When he persisted, they finally moved out of the water up onto the bank. The pilot continued down the wash to warn others. After he left, one of the two women went back into the water and SURPRISE! was caught by a wall of brown water with rocks and trees in it. She survived only by dumb luck when she was pushed against a boulder and was able to wriggle her way on top of it.