No, it's not a joke. The author of this article in The Guardian will send an autographed copy of his latest book to anyone that can identify the U-boats in the picture used in this bogus "documentary". I strongly suspect that the "Cape Town" caption attached to this image is no more to be relied on as accurate than the giant shark fin and tail photoshopped into the background.

I've not posted this because I think the "documentary" is in any way based in fact - read the article that the link goes to - but because I thought someone might be able to identify the boats and win themselves a book.