a deptherapy blog

02 Sep2018


by Dr. Richard Cullen | 02nd September 2018


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Where to begin, there are so many wrecks in the Lagoon that as divers you have a massive choice and the guides are excellent at taking you to the wrecks you want. We knew that we were to complete three dives on the Shinkoku Maru in order to fulfil our commitment to map the coral on one of the wrecks and to carry out a bio mass study. Shinkoku was to prove to be our favourite wreck, a resident Eagle Ray, Turtles, Leopard, Black Tipped Reef Sharks and a myriad of aquatic life + being a wreck in good condition and bedecked with coral made for the perfect dive.

I am grateful to Aron Arngrímsson and Charlie Munns for identifying the Shinkoku as the best wreck on which to conduct our environmental project.

The anchorage is basically littered with wrecks, of ships and aeroplanes. Some ships still continuing Zero bombers and other war materials.

As I mentioned previously some of the wrecks are beyond recreational diving limits but most of our dives lasted between 45 and 60 minutes.


Throughout our build up programme we have stressed that these are ‘war graves’ and must be treated with the same respect as the wreck graves of British vessels sunk during the World Wars. I must admit a feeling of unease that some artefacts have clear be moved from their original location to provide interest and photo opportunities for divers. That they have been moved and arranged so as to provide a focal point of interest for divers leaves me somewhat cold. I and many others share the same view about the roll on, roll off ferry the Salem Express in the Red Sea, which although not a war grave saw many civilians die when the ship hit a reef. Some divers have removed televisions from the wreck and placed them on display.

As for those who plunder wrecks and ‘take artefacts’ they are no more than common thieves plundering war graves.


Most of the wrecks within the Lagoon are ‘Marus’ basically cargo ships. Those built pre-World War II were built with higher grade steel than those built close to and during the war and are better preserved

Some were requisitioned into service but others, were built deliberately by the Japanese for use in war. So ostensibly a liner had been built but they were readily adaptable to be troop carriers or submarine tenders.

The capital ships having fled the anchorage after the US surveillance planes overflight the Marus took the brunt of the attack. There are some small warships, planes and a submarine literally littered around the Lagoon.


(Deptherapy Trustee Andy Searle relaxes on the way to a dive site, with fellow Trustee Ben Lee)


The Shinkoku Maru was built in 1939. Her first voyages were to carry oil from the United States to Japan, prior to the embargo.

The Japanese Navy converted her to a fleet oiler and Shinkoku Maru's most noteworthy mission was her participation in the Pearl Harbor attack as part of Admiral Nagumo's strike force.

In August 1942, she was torpedoed and damaged by an American submarine. She was at anchor in Truk Lagoon at the time of "Operation Hailstone". She survived two days of attacks and two aerial torpedo hits before she finally sank.

The bow gun of the Shinkoku Maru is heavily encrusted with colourful coral.  The soft corals and hydroids are quite beautiful. Her operating theatre is the only one in Truk Lagoon.

(Four pics Shinkoku)




Superstructure: 12m
Deck: 20m
Bottom: 38m

Gross Tonnage

10,020 tons


The Heian Maru was built in 1930 as a large passenger cargo liner. Her maiden voyage was from Hong Kong to Seattle. While on a routine voyage in August 1941, she was abruptly recalled to Japan. Upon her return, the Japanese Navy converted the ship for use as a submarine tender.

It is the largest ship in Truk Lagoon.

The Heian Maru was sunk on the second day of "Operation Hailstone". A torpedo struck her amidships and because of damage already sustained during the earlier raids, the Heian Maru sank quickly.

The Heian Maru lies on her port side. The cargo of the Heian Maru contains many of the deadly efficient Japanese Long Lance Torpedoes, as well as submarine periscopes. Many artefacts can be found throughout this wreck.




Hull 12m
Bottom 36m

Gross Tonnage

11,614 tons


Description: Flying boat

A massive plane wreck, completely upside down with the tail broken away. The engines looked good with no propeller bends, suggesting no impact - i.e. the plane sunk whilst moored. The wings are also quite intact, but the main body and tail are broken up.




Max depth 15m

Betty Bomber

Description: Mitsubishi G4M bomber

The Betty Bomber is upright but it is pretty smashed up. The nose is very broken and the engines are a good 50m swim off the starboard front side where they broke away from the plane and travelled forward. The fuselage was full of glassfish and there was lovely soft corals on the wings. In the cockpit there are seats and fire extinguishers and on the outside of the plane there was a radio and another seat.




Max depth 15m




The Fujikawa Maru was built in 1938 by the Mitsubishi Company as a passenger and cargo carrier.

The Japanese Navy took possession of her in December 1940 and converted the ship to an aircraft ferry. The conversion included a compliment of six inch guns on her bow and stern. These guns were remnants from the Russo-Japanese War.

Just prior to "Operation Hailstone", Fujikawa Maru arrived in Truk and off loaded thirty "Jill" B5N2 bombers onto Eten Airfield. Since these aircraft had been disassembled for shipment, they were unable to help defend Truk and were destroyed on the ground.

The cargo hold still contains Zero fighters.

Today the Fujikawa Maru has an abundance of colourful soft coral and large formations of hard corals. It is regarded by many divers as the most popular wreck of Truk Lagoon.




Superstructure: 9m
Deck: 18m 
Bottom: 34m

Gross Tonnage

6,938 tons


The Gosei Maru was built in 1937 as a coastal freighter.

The Japanese Navy acquired the ship and utilized it as a supply ship for Sixth Fleet submarines. She carried torpedoes and depth charges.

In 1976 many of her torpedoes were destroyed to eliminate possibility of detonation. During "Operation Hailstone", Gosei Maru was sunk by a torpedo. She now lies on a slope. The depth ranges from 8 feet at the stern to 100 feet at the bow.

The rudder and propeller of the Gosei Maru make for excellent photographic subjects.




Hull: 2.4m
Bottom: 31m

Gross Tonnage

1,931 tons




The Sankisan Maru was built in 1942 as a passenger transport. The Japanese Navy acquired control of her in October 1943 and converted the ship to a military transport for use in moving special cargo.

Her sunken cargo contains aircraft engines, medical supplies, and several trucks. This is a popular dive and is frequently visited. Her deck has large anemones and her masts contain heavy growth of soft coral.

The Sankisan Maru is one of the most interesting wrecks in Truk Lagoon. The entire aft section of the ship is completely gone and it is thought that a bomb explosion in the ammunition laden aft hold, led to her sinking.




Deck: 15m
Bottom: 24m

Gross Tonnage

4,776 tons


The Rio de Janeiro Maru was built in 1931as a passenger ship. During peace time the Rio De Janeiro was a passenger and cargo vessel traveling around the world.

In 1940 the Imperial Japanese Navy converted the ship to a submarine tender providing service to the submarines of the Combined Fleet.

After 1943, as the number Japanese submarines had been substantially reduced, the Rio de Janeiro Maru was reclassified as a transport and based in Truk.

During the "Operation Hailstone" attack, the Rio de Janeiro Maru was struck with at least one bomb. She was reported on fire and thought to have sunk on the first day.

The ship lies on her starboard side. It rests on an incline with the stern deeper than the bow. The propellers, rudder, and large stern gun are excellent photo subjects.




Hull: 12-24m
Bottom: 35m

Gross Tonnage

9,626 tons


The Kansho Maru was built in 1938.

The Japanese Navy took control of the ship when the war began and she was put to work shuttling supplies between Japan and the Marshall Islands. Eventually she was retrofitted with a deck gun and augmented with a Naval Gun Crew and Medical Staff for transporting the wounded.

Just prior to the "Operation Hailstone" attack, Kansho Maru was in Kwajalein Atoll delivering supplies when she was bombed by carrier aircraft and took a hit to her engine room. Unable to get underway, Kansho was towed to Truk by the Momokawa Maru.

Both ships were in Truk Lagoon when the U.S. Navy attack began and both were sunk. The Kansho Maru was struck by at least one bomb and an aerial torpedo.

The Kansho Maru sits upright with a slight list to port.




Superstructure: 18m
Deck: 24m
Bottom: 39m

Gross Tonnage

4,862 tons


The Kiyozumi Maru was built in 1934 as a freighter with luxurious passenger accommodations. In November 1941 it was converted to an armed merchant raider. It was fitted with six inch guns, two twin torpedo launchers and anti-aircraft machine guns.

In October of 1943 it was reclassified as a transport. Kiyozumi Maru's most noteworthy mission was as a troop carrier for invasion forces during the Battle of Midway.

Throughout her service she was repeatedly damaged by aircraft bombs and was struck by three torpedoes from an American submarine in 1943. She was towed to Truk and was undergoing repairs at the time of the "Operation Hailstone" attack.

Although she had extensive damage from the submarine attack, it is believed that aerial bombs finally sank her.

The Kiyozumi Maru rests on her port side about 600 yards from Fefan Island.




Deck: 12m
Bottom: 30m

Gross Tonnage



The Yamagiri Maru was built in 1938. In 1941 the Japanese Imperial Navy converted her to a military transport for use in moving special cargo.

The ship saw service transporting war material between the Solomon's and the Caroline Islands until she was hit with two torpedoes from the submarine USS Drum in 1943. The repair of this damage can still be seen on the port side of hold number two.

One of the Yamagiri Maru's most interesting features are the huge armour piercing shells contained in her cargo.

The Yamagiri Maru was sunk by dive bombers that reported several hits and left a huge hole amidships that proved fatal to the ship. She now rests on her port side with the pilot house accessible to divers.




Superstructure: 9-18m
Bottom: 34m

Gross Tonnage

6,438 tons


The Aikoku Maru functioned as a submarine tender, cargo and troop transport ship. On the day of the attack, she was carrying various high explosives in her forward holds including ammunition, aerial bombs, mines and her own shells.

A large anti-aircraft gun is located on top of the aft deckhouse.

The explosion that destroyed the Aikoku Maru was so violent it also destroyed the attacking U.S. Navy aircraft.

(picture of the explosion on the Aikoku)

Almost all of the 945 crew and passengers were killed.




Superstructure: 40m
Deck: 49m
Bottom: 64m

Gross Tonnage

10,437 tons


The Nippo Maru was built in 1936. Her peacetime duties consisted of carrying bananas from Taiwan to Japan.

In 1941 the Japanese Navy pressed her into service as a water transport. As such, she was stationed in Truk to carry water from Dublon Island to the outlying islands where fresh water was scarce.

During "Operation Hailstone", the Nippo Maru was attacked with a salvo of bombs. Her main features include a light tank and artillery pieces on her deck.




Superstructure: 30m
Deck: 40m
Bottom: 50m

Gross Tonnage

3,764 tons


Deptherapy and Rehabilitation
Deptherapy Supporting Communities
Deptherapy’s Coral Conservation Project
Deptherapy Protecting Our Oceans
Deptherapy Educating the Diving World
Personal recollections of Chuuk Lagoon
Diving individual wrecks
The End of a Journey