Shanko Maru and Mini Sub.

Both excellent dives. The Shanko Maru of about  5ooo tons and lying on her starboard side was bombed by the  5th Air Force.

She is an excellent dive and especially a night dive. Lots of soft corals around the upper parts.

The mini sub is approx. 50 meters away and in perfect condition, well worth the dive to explore this fascinating wreck.


 Mini Submarine.

Laying upright in 20 meters is a completely intact Japanese Mini Sub. No one know's the history of this wreck but it is one of only hand full around the world and perhaps the only dive able mini sub anywhere. It is lying some 50 meters from the Mother ship "Shanko Maru" and was bombed by B25's Michael bombers of the Air Apache's on the 16th Feb. 1944 See photo. If you look carefully you will see the sub just before the crew scuttled and just after the sinking of the "mother ship".

The torpedoes are missing but all else is there including the periscope. The cunning tower hatch is open but the opening is to small for divers to enter. Viability is about 15 meter average but vis can improve on the incoming tide in the North West Season.

Attack on the 5461-ton tanker Sanko Maru took place on the early morning of February 16, 1944. It was a combined operation, 41 strafers from the 345th joined three squadrons from the 38th Bomb Group. Six squadrons flew around the west end of New Hanover while Capt. Max Mortensen led the nine strafers from the 500th over the strait between New Ireland and New Hanover, approaching Three Island Harbor from the east. This is where they found Sanko Maru and the midget sub and hovering nearby.

Type A, B & C Midget Submarines--
Views taken in 1942-44

From 1934 to 1944, the Japanese Navy built several dozen midget submarines for combat use. They were originally intended to be carried by larger Japanese ships and deployed in the path of an enemy fleet, where they would disrupt its operations with torpedo attacks. However, during the Second World War, the midgets were used for special operations against ships in enemy harbors, among them the 7 December 1941 Pearl Harbor attack and May 1942 raids on Sydney, Australia, and Diego Suarez in the Indian Ocean. The boats also were employed off Guadalcanal in 1942-43, where they achieved modest success against U.S. shipping, and as shore-based defensive units in the Aleutians and elsewhere in the Pacific war zone.

Type A midgets displaced 46 tons, were 78 feet long and carried two 45cm (17.7") diameter torpedoes. Powered by electric motors, they were capable of very high speeds (about 20 knots), but had very limited range. To increase endurance, the prototype Type B and production Type C boats were fitted with a diesel engine to recharge their electric batteries. They had an additional crew member, were slightly longer and heavier, but otherwise resembled the Type A.

Approximately sixty production Type A midget submarines were built between 1934 and 1942, and given alpha-numeric names in the "Ha" series (Ha-1 through Ha-52 and Ha-54 through possibly Ha-61). The single Type B (Ha-53) and fifteen Type Cs (Ha-62 through Ha-76) were built in 1943-44.

This page features photographs of Japanese Type A, B & C midget submarines taken during 1942-44, and provides links to earlier and later views.


Midget Submarines--

At 12.20 p.m. on August 28, 2002, the Pisces IV and Pisces V, two deep diving submersibles operated by the Hawai‘i Undersea Research Laboratory (HURL), found the Japanese midget submarine which was the first vessel sunk in the attack on Pearl Harbor, December 7th, 1941. HURL is one of six national laboratories comprising NOAA's National Undersea Research Program. It is located at the University of Hawai‘i's School of Ocean and Earth Sciences and Technology. The sunken midget sub was located during the last of a series of test and training dives conducted annually in the military debris fields off Pearl Harbor. HURL is now undertaking its regular four to five month dive season of scientific and engineering dives focusing on fisheries enhancement , coral reef habitats, undersea volcanism, landslide monitoring, acoustic identification of fish and their habitats and other engineering and oceanographic studies.

This midget sub find has been described as the most significant modern marine archeological find ever in the Pacific, second only to the finding of the Titanic in the Atlantic. The Japanese midget sub was one of five attached to five I-class mother submarines and brought from Japan to be launched 5-6 hours before the aerial attack, within a few miles of Pearl Harbor. Each had a crew of two. The subs were battery powered , 78 feet long , 6 feet in diameter and weighed 46 tons. They carried two torpedoes and a scuttling charge to avoid capture. Although experimental in design, they were very advanced for the time. For short periods, they could run at 20 knots. These midget submarines were completed only months before the attack allowing little time for the crews to train. All of the five submarines comprising the advanced attack force were sunk or captured. The type A midget submarines had a series of basic design problems including trim and ballast control and problems both with battery life and battery monitoring. Later redesign, as five man midget submarines of the Koryu class, addressed but did not solve these problems. The Japanese midget submarines although believed at the time to be a potent secret weapon, in actual fact, were never highly effective. So far four of the five original midget submarines attacking Pearl Harbor have been found.


The discovery of the midget submarine confirms the account radioed to naval command at Pearl Harbor at 6:45 am on Dec. 7, 1941 . A Japanese submarine was shot through the conning tower and then depth charged trying to enter Pearl Harbor behind a cargo ship. The crew of the attacking USS Ward , an older style four stack destroyer, saw the midget sub lifted out of the water by depth charges after firing the fatal shot from its four inch side gun. The Ward's crew were Naval reservists from St. Paul, Minnesota. Unfortunately, Naval command in Pearl Harbor ignored the Ward's report and the aerial attack began at 8 am. At the Pearl Harbor investigation, some question was made of the accuracy of the Ward's report. The Ward is now vindicated. The Ward itself was later targeted by the Japanese and sunk in a kamikaze attack, ironically on Dec. 7, 1944, in the Philippines.


The search for the Japanese midget sub has been ongoing for 61 years since it was first sunk. In its latest phase, the Hawai‘i Undersea Research Lab has conducted towed side scan sonar surveys of the debris fields off Pearl Harbor. At the end of World War II, obsolete war material was dumped in 1,000-3,000 feet of water several miles off Pearl Harbor. This included: landing craft, tanks, old aircraft, trucks, barges, small ships, fuel tanks etc. There are on the order of 1,000 significant sonar targets in the area. Sorting through these various targets to identify the most promising ones to dive on as a submersible pilot training exercise has been the work of many years. The Japanese midget submarine although giving a very clear return on the side scan survey was interspersed with other debris on the bottom complicating the search efforts.


The Japanese midget submarine was found in 400 m of water about five miles off the mouth of Pearl Harbor. As it is classed as a military grave site, its exact location is being held by the U.S. State Department. The submarine sits upright on the bottom and is in amazingly good condition as shown in the photos. Both torpedoes are still in place. The submarine has no apparent depth charge damage but does have shell damage on both sides of the conning tower. The port side of the conning tower exhibits what one analyst has identified as shrapnel holes. This would presumably have come from the first shell fired by the USS Ward which exploded near the submarine but did not directly hit it. The starboard side of the conning tower shows a hole from the 4 inch shell fired by the side gun on the Ward as the ship steamed past. Apparently, this shell did not explode on impact as the midget sub conning tower is clearly still in place. While four depth charges were dropped directly on the midget as the Ward passed by, the charges were set to go off at a depth of 100 feet and the submarine was at the surface. The pressure wave created by the 4 depth charges was sufficient to fully lift the 46 ton, 78 foot midget out of the water, but did no visually apparent structural damage. The midget sub sank from flooding through the four inch shell hole.


A number of questions still remain over this submarine, which was the first casualty in the war between the U.S. and Japan. Can and should it ever be raised, perhaps to join the USS Missouri forming the bookends for the Pacific war, that is, the first shot and the final surrender ? Why did the Naval command at Pearl Harbor apparently ignore a confirmed enemy sinking right off its harbor mouth? Why did the Japanese put so much faith in the five midget submarines that they were allowed to lead the Pearl Harbor attack ? After all five of the attacking midget submarines were lost in their first engagement and shown to be ineffective, why did the Japanese Imperial Navy go on to build hundreds of midget submarines most of which were never used ?

Raising the Midget Sub

It is unclear if the submarine will be raised or if its resting site will become a marine sanctuary. Discussions are ongoing between the United States and Japanese governments. It would be technically feasible, although difficult and expensive, to raise the submarine. Recent efforts have raised the sunken Russian submarine Kursk in arctic waters off northern Russia as well as the partial raising of the sunken Japanese fisheries training vessel Ehime Maru off Hawai‘i. Both of these efforts were more complicated and involved larger vessels than the Japanese midget submarine. The Kursk effort involved a nuclear reactor and live and damaged torpedoes. Complications involved in raising this Japanese midget sub include the two torpedoes and the scuttling charge as well as the necessity of maintaining structural integrity on a possibly damaged hull. Initial speculation on a salvage plan has focused on making the midget sub close to neutrally buoyant. This might be done either by pumping compressed air or foam into the hull through the shot hole. The midget sub could then be gently nudged onto a 90 foot long pallet and secured. The pallet would then be gently lifted and towed to shallower, protected waters where divers could arrange a lift to the surface under optimal conditions.


Long before any decision or plans could be formulated to raise the midget submarine, the site will need to be thoroughly photographed and surveyed. There is some possibility that an underwater endoscope such as that used to explore the interior of the submerged wreck of the USS Arizona at Pearl Harbor might be deployed from the Pisces submersibles to explore the interior of the Japanese midget submarine through the shell hole. As the shell hole is quite small, this may prove to be operationally impossible. Further research at the site will certainly clarify the subs condition and provide valuable information for future groups contemplating raising the midget submarine In all cases, future exploration must proceed with the greatest respect and care for this submerged wreck, recognizing it as a war grave site likely containing the remains of the two Japanese crew , the first casualties in the Pearl Harbor attack.

As we learn more about what will become of the Japanese midget submarine, we will post it on this website.