“Even the Jap mini-sub at Pearl Harbor was 78 feet.”
Wow - I always thought of it as two guys (two small Japs at that!) crammed into a 10-foot long tube. Of course I didn’t think too much on it. Engine, transmission, oxygen, etc. But still never would have figured on 78 feet.
Keep in mind that the torpedo tube alone would take up over twenty feet.
I saw an actual Japanese mini-sub, on static display, at the Battleship Cove museum in Fall River, Massachusetts.
It is nowhere near 78 feet long. More like 25 feet long.
Even their late war one man suicide torpedoes clocked in at about 50 feet:
http://combinedfleet.com/ships/kaiten