Shinkoku Maru - Death From the Night Sky

Text & Photos by

Mike Gerken

(as published in Wreck Diving Magazine 2016)

©All Rights Reserved 2016

The sun set on Truk Lagoon on the eve of February 17, 1944. A lumbering 500’ long ship slowly comes to a stop in the choppy waters; its anchor lets loose from the hawsepipe and slips below the tropical waters in search of sandy bottom. The wind swings the ship around and the anchor grabs hold.  The Japanese 10,000 ton fleet oiler, Shinkoku Maru, is now secured to the seabed. Repeated strafing and torpedo runs kept the Shinkoku on the run within the confines of the lagoon, throughout the entire day. Captain Hidenoshin Nakajima instructed his officer, Tokiya Mizutani, to maintain blackout conditions for their vessel during the evening. The crew now rested easier under the cover of darkness, for they narrowly escaped destruction from raiding carrier-based US Naval planes. 

Many other Japanese ships in Truk Lagoon were not as lucky. There were more than 1000 casualties, dozens of ships sunk and hundreds of planes destroyed that day, although the crew weren’t aware of the tally of death and destruction, they could see it all around them. The smell of burning ships fouled the air and dense black smoke blotted the sky. The crew of the Shinkoku were a few of the lucky ones, for the moment.  Little did they know that the United States Navy was not finished with Truk Lagoon. The blackness of night would not protect them for what was about to come.

Turning her bow into the wind, the aircraft carrier USS Enterprise prepared Torpedo Squadron Ten for take off. They were 100 miles from Truk Lagoon, the Japanese “Pearl Harbor” of the Pacific. This naval stronghold was a highly strategic base for the Japanese and it was essential for the Americans to neutralize its offensive capabilities in the central Pacific.  The Enterprise, along with the rest of Carrier Task Force 58, just spent the day battering the Japanese from the air in a raid codenamed “Operation Hailstone” but, their work was far from over.

The pilots and crew of the Grumman TBF Avengers stared down the runway into the night sky; the sun would not rise for another four hours. The order from the commander was given, launch all planes; the mission is a go! One by one the twelve TBFs armed with four-500lb bombs launched from the deck of the carrier on their way to face the enemy of Truk Lagoon.

The crew trained for months for what was to be the first ever carrier based minimum altitude night raid in history. The theory was, the planes would fly at low altitude with the cover of darkness, evading enemy ground fire, thus allowing for increased accuracy of bomb drops. Would they make a successful mark or would the raid go down in the annals of history as failure? Tonight the crew of the Avengers would be put to the test.

The TBFs made radar contact 20 miles out from Truk. They approached the lagoon at an altitude of 500 feet and rendezvoused at two separate locations along the outer reef. At one-minute intervals a single plane would enter the lagoon in search of suitable targets. Even at only a ¼ moon the Japanese were able to spot them due to the inefficient flame dampeners on the engines, anti-aircraft fire from the Japanese below was accurate.

With the use of radar, the planes searched carefully for suitable shipping to attack. However, the many small coral islets within the lagoon, that gave the appearance of ship signals on the radar screen, hindered their search. The crew improvised and made visual contact with their targets and utilized radar to exact their bomb drops.

One Avenger discovered a lone fleet oiler anchored in the center of the lagoon. Tankers and oilers were considered prize targets.; Wwithout precious fuel to run their war machines, the Japanese Imperial forces would be crippled. Approaching the target at an altitude of a mere 250 feet, the bombardier lined up his sights and prepared to deliver a deadly surprise from the night sky on the unsuspecting ship below.

Officer Mizutani rested in the foreword section of the Shinkoku after working diligently with his engineering crew on repairing the steering gear. It was 0200 hours on February 18, 1944, when he suddenly heard a plane overhead followed by the sound of a bomb being released. Seconds later, there was an explosion from astern; the lights immediately went dead. A fireball shot up through the crew quarters in the stern incinerating 25 men as they slept. (A 500lb bomb with a 4 second delayed fuse had struck the water directly next to the Shinkoku's port side and plunged deep below the waterline before exploding, placing a massive hole in the hull next to the engine room.)

Mizutani raced to the stern along the catwalk on the port side with the other survivors and discovered steam rising from the poop deck, by then the ship began to settle by the stern. Anxious and upset, the men, began to climb into rubber rafts while ignoring the lifeboats hanging by their davits. Drifting with the prevailing winds and paddling with their hands, the men made their way to a small island in the central part of Truk Lagoon called Eot. It was 1100 hours. Once ashore, Captain Nakajima, Officer Mizutani and crew rested under a coconut tree and asked themselves. “How did the Americans spot us at night? How could they have such a good eye?” The two of them were not aware that the allies had radar technology that could be used on such small aircraft.

The next day, the captain and all the officers were evacuated from Truk Lagoon on a destroyer flotilla while Mizutani remained behind to clear up ships business. Each day he would walk to the hilltop, look out on to the lagoon and watch his ship slowly vanish below the waves. It was a somber moment. The Shinkoku Maru was esteemed by the Japanese for being one of the fleet oilers for the task force that raided Pearl Harbor on that infamous day in December of 1941. It took four days before the Shinkoku would succumb to the rising waters. There she would sit on the bottom of the lagoon, an eternal silent grave for 25 souls.

The night raid was considered a huge success for the US forces. Torpedo Squadron Ten was responsible for scoring 13 direct hits on enemy shipping which destroyed or sank 8 and damaged 5 merchant vessels including the Shinkoku Maru. Only one US TBF was reported missing and presumed shot down. When the numbers were analyzed, they revealed that 4.6 times as many hits could be expected with a given number of planes when they attack at night instead of in daylight.  This was yet another blow to the Japanese war effort in the Pacific. They were losing the war, due in part to lagging behind in the technology race with their enemies.

Today, the Shinkoku Maru is one of Truk Lagoon’s most famous wreck dives. Her sheer size, penetrability, dense marine life and interesting artifacts continue to awe divers who travel from around the world to experience this underwater relic from WWII.  Whether you are a novice or seasoned expert, this wreck has much to offer all divers.

I vividly remember my first dive on the Shinkoku Maru. All of my senses were peaked during the experience. I made the long swim aft and dropped over the port side in search of the bomb blast hole next to the engine room. Watching my depth gauge tick past 110’, I could make out the massive hole in the ship below me. The Shinkoku had completed transferring its supply of crude oil prior to the raid, causing the ship to ride high in the water. Because of this and the use of delayed fuse, the bomb descended deep along the hull before detonating, giving the impression that a torpedo was the culprit and not a 500lb aerial bomb. (The TBF Avengers did not use torpedo’s on the night raid. This was evident by the information in the official report filed with the Pacific Fleet on February 26, 1944 by Commander W.I. Martin of Torpedo Squadron Ten.)

Swimming through the hole in the hull of the ship was not an issue; it was more than 10 feet across. Once inside, I made my way around large pumps and twisted metal and found the entrance in to the generator room in the deepest recess of the ship. The near proximity of the generator room to the blast hole would have explained why the power went out right after the explosion was heard. A wall of water would have flooded the room instantly, not to mention the blast must have damaged the generators and electrical components themselves. I swam past three gens and looked for an exit to the next level of the engine room. I found a ladder and followed it up and swam past the bottom of the diesel powered cylinders. I could imagine these behemoth connecting rods and drive shaft clunking away at top speed trying to avoid US bombs on the first day of the raid on Truk.

After a few more minutes of inspection, I found myself climbing another ladder into the upper part of the engine room, where the sight of ambient light could be seen penetrating from the sky lights 20 feet above me. I could breath a little easier now that sunlight marked an exit point to safety above. I made a few laps around the massive steel cathedral and noticed an open door. I headed in and found a machine shop complete with drill press and grinding stones and other equipment scattered about on the floor. Above the machine shop, I noticed another entrance on the port side and after squeezing through the tight door, I found myself in the eeriest part of the wreck; the aft crew quarters. Here was the location of a grisly scene; 25 men killed by the blast, most while they slept.

I swim down the companionway and headed towards a glow of light trying not to let my thoughts dwell too long on the men who perished here. Shimmying my way out of the door, I find myself on the deck level heading forward. The marine life is thick all around me.  A loan spotted eagle ray, seeming to demand my attention, swims past me repeatedly lapping the standing smoke stack. I continue on down the amidships deck and see the forward super structure. My depth is a modest 75’ so I continue to explore the internal areas of the ship. I find within a Japanese style bathing area with porcelain basin, still bright white. There are cables, ductwork, radiators and pipes, all exposed due to the inner walls rotting away many years ago.

On the lower level, I find evidence that the Shinkoku served not only as an oiler, but a hospital ship, as well. There is an operating room: table, autoclave, sink and many medicine bottles lying about. I’m told that, years ago, wheelchairs could be seen stacked in the corner. Time must have taken its toll on these fragile artifacts. There is no evidence of their existence anymore.

I head up through the open stairwell to the officer quarters and manage to find the location where Tokiya Mizutani once lived. Mr. Mizutani survived the war and left his stories behind in the form of letters he wrote to a sport diver in the 1970’s. I have used his accounts of the sinking of the Shinkoku Maru in assisting me assemble the final hours of the ship.  

One more level up into the super structure and I’m looking into the bridge. The ceiling is mostly gone now, allowing plenty of light to penetrate within. The windows of the wheelhouse are covered with stunning sponges, sea fans, soft corals and large clams. Along with this wide spectrum of color, I find three bridge telegraph annunciators as well as the compass binnacle and helm stand. My depth is only 40 feet. A diver could spend all day in these shallow depths exploring, but still. I wanted to head to the bow to have a look at the forward gun.

My trip to the bow is etched in to my memory. Never before, nor since, have I seen an underwater Eden as I had at that moment. Dozens of beautiful Magnificent Sea Anemones are seen everywhere with many overlapping one another. With spans measuring more than a meter across, these creatures are likely as old as the wreck itself.  Enormous sea fans reach out in all directions. Soft corals of yellows, purples, pinks and whites adorn the mast, booms and anything of structure that it can latch on to. A school of big eye-trevally encircles the tip of the bow and an occasional tuna cruises the perimeter in search of a meal. The tropical fish species here are diverse and abundant. My previous moments on this dive were occupied with the history and the functionality of the vessel prior to her sinking. I thought of the men and the lives they lived and, for some, their tragic end Now, I’m lost in a surreal moment of environmental wonder. The death of this once fine ship has now sprung new life.

I make my way up the port side catwalk that I've nicknamed, “Anemone Row” and find at the end the foredeck with what appears to be a mound of coral on top of an elevated platform. Upon close inspection it becomes apparent that underneath all the dense coral growth there is the bow gun. Not much is visible of this weapon that could have been used on Japanese warships during the Russo-Japanese War at the turn of the century. The old warships were scrapped and the guns were recycled and utilized on the decks of merchant ships two wars later.

My first dive on the Shinkoku Maru was etched in to my memory. Since then, I have likely logged more than 150 dives on this wreck and continue to discover something new each time I delve into her. The Shinkoku has an interesting history to bestow upon the discerning diver and, with true duality, is a remarkable marine ecosystem to lose oneself in. The Shinkoku Maru will leave you desiring to visit her again and again to learn more of her stories and eyewitness one of the worlds most beautiful wreck dives.

Mike Gerken is a published professional underwater photographer, documentary filmmaker, writer and captain of the M/V Odyssey in Truk Lagoon. He markets his work through his company Evolution Underwater Imaging. Visit to learn more about Mike and to see his complete portfolio.

For more information on Truk Lagoon watch the documentary , “The Wrecks of Truk Lagoon” produced by Mike and available for purchase on DVD at or digital download at

Article References

National Archives and Records Administration; Torpedo Squadron Ten Report on Night Radar Minimum Altitude Bombing Attack on Enemy Shipping in Truk Atoll; February 26, 1944; Written by Commander Torpedo Squadron Ten, W.I. Martin

Letters of correspondence between Mr. Tokiya Mizutani &and Mr. Robert DeRRuff 1976 thru 1979; translated by K. Nakahara

Video interview with Kimio Aisek; founder of the Blue Lagoon Dive Shop, Chuuk, Micronesia; filmed approximately in 1986 by Jim Church; video courtesy of Mike Haber and Mike Mesgleski of Jim Churchs School of Underwater Photography.