The documentary is called Hitler's Lost Sub and can be purchased on Amazon right along with Gentile's book...probably on the same page
There have been alot of very heated threads comparing Gentile's book with Shadow Divers. That may be why you haven't had alot of replies to this thread and I too will opt out of comment unless some of the Gentile proponents show up with their ridiculous comments/baseless accusations
I know of one thread that was even pulled by Doc due to it's content of viscious name calling and accusations. Do a search and you can find several threads.
There is a thread titled reel versus no reel...something like that in the wreck diving sub forum, wreck exploration...It seems there are not very many proponents of progressive penetration. I would venture to say it's probably an 80/20 for/against.