Hawaii Undersea Research Laboratory light cruiser St. Louis Helm Boggs belt armor Pearl Harbor midget submarine Hawaii aerial torpedoes
In 1992, 2000, and 2001 Hawaii Undersea Research Laboratory's submersibles found the wreck of the fifth midget submarine lying in three parts outside Pearl Harbor. The wreck was in the debris field where much surplus U.S. equipment was dumped after the war, including vehicles and landing craft. Both of its torpedoes were missing. This correlates with reports of two torpedoes fired at the light cruiser St. Louis at 10:04 at the entrance of Pearl Harbor, and a possible torpedo fired at destroyer Helm at 08:21. There is dispute over this official chain of events though. The "torpedo" that St. Louis saw was also reportedly a porpoising minesweeping float being towed by the destroyer Boggs. A photo taken by a Japanese naval aviator of Battleship Row during the Attack on Pearl Harbor was declassified in the 1990s and publicized in the 2000s to the public. According to numerous historians and naval architects this photo shows that the fifth midget submarine appeared to have fired a torpedo at West Virginia and another one at Oklahoma. These torpedoes were twice the size of the aerial torpedoes so it was possible that both torpedoes fired by the unaccounted for fifth submarine heavily contributed to the sinkings of both ships and especially helped to capsize Oklahoma because Oklahoma was the only battleship that day to suffer catastrophic damage to her belt armor at the waterline from a torpedo. Admiral Chester Nimitz in a report to Congress confirmed that one midget submarine's torpedo (possibly from the other midget submarine that fired torpedoes but failed to hit a target) which was fired but didn't explode was recovered in Pearl Harbor and it was much larger than the aerial torpedoes.

