Wendy, I don't doubt that people have died when diving in caves while untrained. I will also venture to say that people have died who did have formal training in cave diving.
I don't deny that cave diving is a speacialty like no other (maybe I should say overhead environments).
When I was in school in the Navy, I remember one of my teachers trying to explain to a classmate how a particular radar tracked a helicopter. He was having no luck. After reading about it in the tech manual I asked if I could attempt to explain it, after my explanation the instructor said "now I think I understand how it works". An instructor teaching from a book someone else wrote doesn't ensure the instructor understands all aspects of the written material. It all has to do with reading comprehension (a lost skill here in america).
What makes the info more valuable because it came from a humans mouth instead off a written page? If your reading comprehension skills are good...nothing. How do you know that the person teaching you the book understands or comprehends what is actually saying. This is kind of a twist in the learing community...books are bad, but a teachers interpretation of said written book is good? I disagree.