I came across a brilliant web page titled 'TOM PAINE'S JOURNAL', Tom was a US submariner responsible for taking possession of Japan's i-400 underwater aircraft carrier submarine at the end of the war and sailing it to the US for examination. There are some fabulous stories here but the one I like was when the Navies Health Safety officers stopped them from departing due to the disgusting state of the submarine, here's a quote:-
After she was taken over from the Japanese on her way home from patrol you can imagine that the I-400 required a massive clean-up from stem to stern. The field day started with all hands moving aboard the U.S.S. Proteus, after which cylinders of fumigating gas were opened in every compartment and the boat sealed. Next morning bushel after bushel of dead rats and cockroaches were swept up. I'd noted with some revulsion on the Ha-boats the occasional rat leaping through a hatch from compartment to compartment, and hordes of scurrying roaches when a light was switched on, but I'd no idea that these boats carried so many verminous shipmates on patrol. If the I-400 had been rigged for dive when the rats and roaches were thrown overboard the Diving Officer would have had to order: Flood two hundred pounds to Auxiliary Tank from sea.
These Jap subs were huge carrying 3 airplanes and having a displacement of 6.500 tonnes, I highly recommend this fascinating article:-
http://www.pacerfarm.org/i-400/