Below the Restless Waves
This local story about the finding of a WWII-era sunken Japanese submarine off the coast of O'ahu is starting to get national attention so maybe it will be of some interest to you. It seems that near the end of World War II, the Japanese built three huge submarines capable of carrying, launching, and recovering aircraft.
By huge I mean about 400 ft. long (about 122m). By comparison, a present day Virginia class attack submarine such as the USS Springfield SSN 774, is only 377 ft. (about 114m) long. While it is true that the current Ohio class ballistic missile submarines, at 560 ft. (about 171m), are longer, you have to remember we are talking about 1940s technology here. Fully loaded with fuel, these "Sensuikan Toku" class of diesel/electric submarines could sail one-and-a-half times around the world without refueling.
Each of these submarines held three torpedo-bomber aircraft with enough parts to build a fourth. The aircraft were hangered in a water tight compartment until made ready for flight. Within seven minutes, the planes wings could be unfolded, float pontoons attached as landing gear, and the plane launched, via catapult (see the illustration below).
The original mission was to fly over the west coast of the US and drop rats/insects infected with bubonic plague, cholera, dengue fever, and typhus. This mission was changed to a secondary target of the Panama Canal. This, in turn, was changed to a third target closer to the Home Islands.
Two of these submarines were captured at sea, a week after the Japanese surrender in 1945. These two, along with some other captured Japanese submarines were sent to Pearl Harbor for evaluation. While there, our allies the Soviet Union decided they also wanted to study these subs. Things being what they were at that time, the US decided to sink the subs off the coast rather than let the Russians have a look.
There they rested until a University of Hawai'i research submarine, Pices, came upon the monster submarine last week Thursday (see the photo below).
For more information on these leviathans follow this link here.
Aloha!