Most of the other fifty are unaccounted for, although three were captured in Sydney (Australia), and others in Guam, Guadalcanal, and Kiska Island, accounting for some of the other hull numbers.

The submarines were fitted with 1300Ib warheads to be used in suicide attacks, they were intended to ram enemy ships in the event of a mainland invasion but were believed to have never been used.

[8] A second Pearl Harbor midget submarine, No.18, was located by U.S. Navy divers and US Marine Divers in training including Laurence McInnis and Fred Stock of A Company, 3rd Recon Battalion, off Keʻehi Lagoon east of the Pearl Harbor entrance on 13 June 1960.

[1] The midget submarine attacked by Ward (DD-139) at 6:37 a.m. on 7 December, No.20, was located in 400 meters (1,312 feet) of water five miles outside Pearl Harbor by a University of Hawaiʻi research submersible on 28 August 2002.

It was visited at approximately 6:30 am local time, by an Okeanos explorer ROV, on 7 December 2016, 75 years after it was sunk.

16 describing the air attack on Pearl Harbor as successful, and at 00:51 on 8 December they received another message that read "Unable to navigate.

In 1992, 2000, and 2001, Hawaiʻi Undersea Research Laboratory's submersibles found the wreck of a midget sub lying in three parts three miles south of the Pearl Harbor entrance.

The wreck was in the debris field where much surplus U.S. equipment was dumped from the West Loch Disaster of 1944, including vehicles and landing craft.

In 2009, a research team assembled by the PBS television series Nova positively identified the sub as being the last, No.16, of the 5 Ko-Hyoteki that participated in the 7 December 1941, attack, plioted by Ensign Masaji Yokoyama and Petty Officer 2nd Class Sadamu Kamita.

[14] Some have suggested that circumstantial evidence supports a hypothesis that No.16 successfully entered Pearl, fired its torpedoes at Battleship Row, and fled to the relative quiet of neighboring West Loch, and possibly was scuttled by its crew.

When a series of explosions sank an amphibious fleet being assembled in the Loch in 1944, it is suggested the remains of the sub were collected and dumped in the subsequent salvage operation, which was kept classified as secret until 1960.

A war time report from Admiral Nimitz confirmed the recovery of at least one dud torpedo of the type employed by the midget submarines.

The outer-harbour defences detected the entry of the first midget submarine, No.14, at about 8 pm, but it was not identified until it became entangled in an anti-torpedo net that was suspended between George's Head and Green Point.

Before HMAS Yarroma was able to open fire, the submarine's two crew members destroyed their vessel with demolition charges and killed themselves.

Some four hours later, having recovered, it entered the harbour, but it was subsequently attacked with depth charges and sunk in Taylor Bay by vessels of the Royal Australian Navy.

I-20 and I-16 launched two midget submarines, one of which managed to enter the harbor and fired two torpedoes while under depth charge attack from two corvettes.

The second midget submarine, No.16b, was lost at sea and the body of one of its crew was found washed ashore a day later.