Ship History
Sankisan Maru was owned by Nippon Yusen Kaisha (NYK) and used as a passenger and cargo vessel with a 6,000 ton capacity. Prewar, used to transport rice from Indo-China (Vietnam), Korea and China. During one trip from Japan, transported six locomotives and 54,000 yards of canvas to Phonom Penh.

Wartime History
Requisitioned by the Japanese Army as a cargo vessel (AK) to transport military cargo armed with machine guns for anti-aircraft defense.

On June 4, 1942 departed Tokyo Bay bound for Marifu as part of a convoy with Eiyo Maru, Hokko Maru and Taian Maru escorted by destroyer Hatakaze.

On September 5, 1943 departs Moji bound for Takao as part of convoy no. 194 with Juyo Maru, Kyokuto Maru, Tsushima Maru, Wazan Maru, Yulin Maru, Zuiyo Maru plus another unidentified merchant ship, escorted by destroyer Sanae.

On October 26, 1943, departs Yokosuka as part of convoy No. 3026 with Choan Maru No. 2, Soyo Maru, Awa Maru escorted by Fukue. On October 28, 1943 Sankisan Maru suffers a mechanical break down and is escorted by Fukue to Chi Chi Jima arriving two days later at 1:30pm and repaired.

During 1943 operated off Saipan. On November 18, 1943 departs Truk Lagoon at 10:00am as part of a convoy with Hinode Maru escorted by minesweeper W-28. On December 2, 1943 at 6:00am departs Chi Chi Jima as part of a convoy with Hinode Maru escorted by Patrol Boat No. 46 and minesweeper W-28 bound for Yokosuka.

During January 23-31, 1944 at Yokosuka. On January 31, 1944 at 7:00am departs Yokosuka bound for Truk Lagoon as part of a convoy with Zuikai Maru, Ryuko Maru and and Taiho Maru escorted by subchasers CH-29, CH-64 and auxiliary subchaser Takunan Maru No. 6 and and auxiliary minesweeper Keinan Maru. En route during February 1944 subchaser CH-32 joins the convoy to provide additional escort. On February 12, 1944 Sankisan Maru arrived at Truk Lagoon.

Sinking History
On February 17, 1944 during "Operation Hailstone" anchored to the west of Uman Island in Truk Lagoon loaded with ordnance and supplies. During USS Bunker Hill Strike 3D, four SB2C Helldivers from VB-17 attacked Amagisan Maru then attacked this vessel, hitting it in the forward deck with a 1,000 lb bomb and strafed by two escorting F6F Hellcats from VF-18 firing 400 rounds at an "AK south of Fefan Island".

The next day on February 18, 1944 during "Operation Hailstone" this vessel was again targeted by USS Bunker Hill Strike 3A by five SB2C Helldivers attacked "an AK at anchor about a half mile west of Uman Island " and scored a hit to the aft with a bomb or torpedo that caused an explosion that damaged the midship and caused the vessel to sink. The stern section was blown off and sank into deeper water. Possibly, the hit or fire caused ordnance stored in the aft hold to explode. The explosion caused a crater in the sea bed. The precise history of the sinking is not clearly documented in Japanese records.

Shipwreck
Sankisan Maru is sunk to the southwest of Uman Island and southeast of Fefan Island in Truk Lagoon. The shipwreck of Sankisan Maru has been known since the war as one of the forward masts is 12' above the surface, until it broke off. Until identified known locally as "Uman one-mast wreck". The vessel is upright on the bottom with her bow pointed towards nearby Uman Island and the stern detached in deeper water.

Since the earliest days of SCUBA diving, this shipwreck has been dived. During 1969, Jacques Cousteau documentary The Undersea World of Jacques Cousteau: Lagoon of Lost Ships includes footage of Sankisan Maru.

The fore ship is relatively intact. On the deck are the remains of three trucks, two on the port side opposite cargo hold no. 1 and another to starboard. All the trucks were heavily damaged in the sinking and only their engines, radiators and frames remain.

Cargo hold no. 1 was filled with munitions including 7.7mm bullets in wooden crates plus a smaller quantity of 20mm cannon ammunition, 12" detonators, 284 depth charges under tarps and a few 4.7" artillery shells. During 1974 with recreational diving on the shipwreck, the munitions in cargo hold no. 1 were removed using a crane and LCU that lifted out the depth charges and artillery shells. In total, 284 depth charges were removed and several 4.7" shells. During the recovery, picric acid from the explosives inside the munitions leaked out into the water and caused the marine growth on the wreck to die in the next several years.

Cargo hold no. 2 contains the remains of several Izuzu Type 94 TU-10 1.5 ton 4x2 trucks, their bodies corroded with only the engines remaining. The hold also contains aircraft parts and three radial engines plus a compressor. This hold connects to the no. 3 hold.

The midship section is badly damaged from the explosion and sinking. The funnel is crushed flat and there are two boat davits with soft corals growing on them. Some of the superstructure is hanging off the starboard side and rests on the bottom with two machine guns. The upper decks of this shipwreck have deteriorated due to SCUBA diving and dynamite fishing by locals. The stern section with the propeller and rudder is at a depth of 150' and rarely dived.

References
Previously, this shipwreck has been misidentified as a vessel as Red Hook/Commercial Traveler/Nelson Traveler/Point Estero/Stero before capture by the Japanese during 1942, this is incorrect.
The Undersea World of Jacques Cousteau: Lagoon of Lost Ships includes footage of this shipwreck
WWII Wrecks of Truk Lagoon pages 4, 6, 140 (photo), 141, 156, 163, 165, 266, 268 (map), 434-439, 512 (index)

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Last Updated
December 1, 2022