The missing fifth midget sub that took part in the Pearl Harbor attack has been found, and for what surprisingly appears to be the second time. This episode of Nova was broadcast a few years ago, though I find it makes for interesting viewing, especially since the "explosives" testing was performed literally across the road from me, at the Earle Naval Weapons depot in Colts Neck, NJ.
http://www.youtube.com/watch?v=vxDueofD_3U