In case anyone wants to read up on S-Boat history-
Includes interior shots on several boats-
http://www.rddesigns.com/subs/s-boats.html
And of course there's "Pigboat 39" the book about S-39 (in case you're wondering where they got the scene of the skipper wearing the Nor'wester at the periscope in "U-570")...
A first hand S-boat account-
http://www.geocities.com/goliverjones/home.htm
(sub school portion starts on page 8).
S-boat histories-
http://www.history.navy.mil/danfs/s-list.htm
Yours, Mike