The Seiko Maru was a 394ft/119m, 5,385-ton aft-engine cargo ship built in 1940 for the prestigious Dairen Kisen Kabushiki Kaisha. The word ‘Maru’ designates a merchant vessel. She provided worldwide cargo hauling from Japanese ports to America, Australia and Europe, and passenger service between China and Japan. Following her requisition by the Japanese Navy, the Seiko Maru shifted from worldwide cargo shipping duties to transporting war material between the Empire and the Inner South Seas.
The ship proved very difficult to conquer as she survived attacks by submarines USS Porgy and USS Steelhead, which listed the Seiko Maru as officially “known sunk” on July 31st 1943. However, intelligence reports indicate that while she was enroute from Yokohama to Truk on the night of July 31st 1943, the submarine USS Porgy made a surface periscope attack on a convoy of which she was only a part, sinking the Mogamigawa Maru. Later on the next day, as the Seiko Maru was picking up survivors, the submarine USS Steelhead torpedoed her.
Although crippled and floating dead in the water, she was eventually towed 243 miles to Truk for repairs.
On February 17th 1944 the Seiko Maru was again difficult to sink. She was located at anchor by attacking aircraft from the USS Enterprise approximately 800-1,000m due east of the northern tip of Eten Island. She was hit by bombs on both sides of the aftship near the rear hold resulting in large explosions that reportedly blew out the sides of the ship. Photos taken shortly after show her stern nearly awash with heavy black smoke billowing up from the ship. She was attacked later that day by planes from the USS Essex and was hit by a 500 lb. bomb amidships. The next day a plane from the USS Bunker Hill missed her with two bombs, but the Seiko Maru was still afloat when air operations ended mid-day on February 18th. However, she finally succumbed to the damage inflicted upon her, sinking the next day surprisingly with the loss of only one man.
The Seiko Maru rests fairly deep on an even keel. Her forecastle deck lies at 120ft/36m with the main deck at 140ft/42m. The bottom of the holds reaches 155 ft/47m and the sea bottom is at 185/56m feet. There is a field artillery piece on the bow and torpedo bodies in Hold No. 1. The wreck is in a reasonably good stage of preservation, but due to its depth, it is rarely visited.