I hope weapons is the best place for this post. I found this just amazing!
On Thursday March 17th during a training exercise on a new navigation system, the Hawai‘i Undersea Research Lab (HURL) discovered the wreck of the Japanese World War II submarine I-401 sunk during target practice in 1946. The wreck of the I-401 was found using the new track Link 5000 HA navigation system provided by NOAA's Ocean Exploration Program. The wreck was found in 870m of water off Barbers Point, Oahu. The I-401 was one of 3 aircraft carrying submarine built in 1944. These were the largest diesel electric submarines ever built comparable in size to the largest present day nuclear submarines. They were 20 years ahead of their time.
http://www.soest.hawaii.edu/HURL/I-401.html
and more at
http://en.wikipedia.org/wiki/I-400_class_submarine
and
http://www.pacerfarm.org/i-400/
Evidentally they where using one plane versions in the beginning of the war with great success.
I consider myself a bit of a WW2 buff and this info comes as a complete surprise!