Chuuk Lagoon
Diving in Chuuk Lagoon (Truk)
Chuuk Lagoon, previously known as Truk Lagoon, is located in the Federated States of Micronesia. It’s renowned as one of the world’s most significant underwater museums due to its large assembly of World War II shipwrecks. Thie waters of the lagoon encapsulates a pivotal moment in military history during Operation Hailstone in February 1944.
Chuuk Lagoon was a major forward operating base of the Imperial Japanese Navy, located in the central Pacific Ocean. The lagoon’s geography offered a natural fortress, with a protective barrier reef encircling a bay that served as a safe haven for Japanese naval operations. Due to its strategic importance, it was heavily fortified with defences and served as a logistical hub throughout the early stages of the Pacific War.
Operation Hailstone
Executed on 17th and 18th February 1944, Operation Hailstone was a massive surprise attack by the United States Navy against the Japanese fleet stationed at Truk Lagoon as it was then called. Planned as a counterpart to the raids against Tarawa and aimed at neutralising Japanese operational capabilities in the Pacific, the operation involved a series of air and sea attacks over two days.
Carrier-based aircraft from the United States Navy, including bombers, torpedo planes, and fighters, launched continuous waves of attacks against Japanese ships and aircraft. The attack was devastatingly effective, catching the Japanese largely unprepared and resulting in significant destruction of naval and air power.
Ship graveyard
The aftermath of Operation Hailstone left behind an extensive array of sunken ships, aircraft, and other military equipment, transforming Chuuk Lagoon into one of the largest underwater archaeological sites in the world. More than 60 ships and 275 aircraft were sunk or destroyed, many of which remain almost intact to this day. The wrecks include a variety of auxiliary ships, freighters, destroyers, and submarines, along with fighter planes, bombers, and seaplanes.
Perhaps one of the most incredible things about the wrecks of Chuuck lagoon, is that after the war it was largely forgotten about. It was actually Jaque Cousteau that rediscovered the wrecks. It was well documented at the time that Cousteau’s team took a huge number of artefacts from the wrecks. The whereabouts of which are thought to be in a warehouse in Paris.
Among the notable wrecks are the Fujikawa Maru, a converted passenger and cargo ship that served as an aircraft ferry and repair ship, and the oil tanker Shinkoku Maru. The wrecks are scattered across the lagoon at various depths. Many sit in shallow waters suitable for recreational divers, but others are only accessible to tech divers.
The wrecks have become thriving marine habitats, providing shelter and substrates for coral growth and an abundance of marine life. This transformation from instruments of war to life-supporting ecosystems offers a poignant narrative on the power of nature to reclaim and repurpose even the remnants of human conflict.
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Getting to Chuuk Lagoon
There’s no avoiding the fact that unless you live in the Philippines or Guam, getting to Chuuk Lagoon is a very long journey. From the UK it’s usually a flight to Manilla, then a flight to Guam, then the flight to Weno. From the US you can get a flight from Hawai with American Airlines that stops at Weno. Or a flight from somewhere in the US to Guam, then another to Weno. If you’re flying from New Zealand or Australia, you can fly Air New Guinea to Port Moresby and transfer from there. You’ll be on another planet by the time you arrive regardless.
Whether you’re diving on a liveaboard or from one of the hotels, they will usually arrange to pick you up from the airport. There’s really nothing in Weno, the odd supermarket, but nothing else. It’s quite a depressing place, very run down with a lot of poverty and alcoholism. Definitely not a place to wander around in the dark.
Fujikawa Maru
The Fujikawa Maru, originally built in 1938 by Mitsubishi Corporation in Nagasaki, Japan, was a cargo ship that also served as a passenger liner between Yokohama and South America. However, with the outbreak of World War II, the ship was requisitioned by the Imperial Japanese Navy. It was converted into an aircraft ferry, tasked with transporting aircraft parts and other war materials crucial to Japan’s military efforts in the Pacific theatre.
Circumstances of the sinking
During Operation Hailstone, the Fujikawa Maru was in the process of being unloaded. As such, it was a sitting duck. It was struck by multiple torpedoes and bombs dropped by U.S. carrier-based aircraft. The bombs that hit the Fujikawa Maru caused catastrophic damage. They penetrated the ship’s hull and reached the lower cargo holds, which not only contained aircraft but also ammunition and fuel, leading to secondary explosions that sealed the fate of the vessel. The fires from these explosions would have made any firefighting efforts futile, contributing to the rapid sinking of the ship.
The wreck today
The wreck is located in relatively shallow waters, making it accessible to divers of varying skill levels. The top of the superstructure is at a depth of about 9 meters, while the deepest part of the hull reaches down to approximately 34 meters. These depths allow novice and experienced divers to explore different parts of the ship comfortably. Divers can swim through the bridge and deck areas.
Perhaps the most fascinating aspect of the Fujikawa Maru is its cargo holds, which still house the remnants of fighter aircraft, including several Mitsubishi A6M Zero fighters. They lie in various states of assembly. The holds also contain munitions and some personal effects of the crew, such as gas masks. The engine room provides a deeper dive into the mechanical workings of the ship. The engines, intricate pipework, and machinery are encrusted with marine life and coral, The iconic R2D2 is located here.
San Francisco Maru
The San Francisco Maru was a Japanese merchant cargo ship, officially classified as a Type 2D standard freighter. It played a significant role in Japan’s wartime logistical operations, transporting various military cargoes, including vehicles, ammunition, and other war materials across the Pacific.
Circumstances of the sinking
The San Francisco Maru met its demise on February 18th, 1944, during the second day of attacks of Operation Hailstone. It was struck by a 500lb bomb, dropped by an Avenger from the USS Essex. The bomb created a huge fire, and eventually, it sank- stern first. 5 members of the crew were lost. It’s often called the “Million Dollar Wreck,” because it was full of expensive cargo.
The wreck today
The San Francisco Maru rests upright on the seabed at a depth of approximately 63 meters (207 feet). The top of the deck is at 50m and the shallowest part of the wreck is the masts at 32m. Such depths make it a technical dive, though you’ll see local dive guides leading customers, all on single tanks.
On the starboard deck there are two type 95 Ha-Go tanks. Next to the tanks on the starboard side is a 1.5 ton 4×2 Isuzu Type 94 flatbed truck. On the port side sits another tank. The cargo holds contain various munitions, bombs, and artillery shells. Hold number two has two partially collapsed flatbed trucks. There used to be a lot of hemispherical mines in the cargo holds, but they were removed by locals. One of the highlights of the wreck is the large engine room, which is easily acceible through the skylights. Towards the stern, evidence of where the bomb hit is visible. Hold number four contains torpedoes, and the doghouse at the stern, though collapsed, contains lanterns in various states of preservation.
Aikoku Maru
The Aikoku Maru was constructed at the Mitsui Tamano shipyards in Okayama Prefecture and launched in 1940. With a displacement of approximately 10,437 tons, it was a significant vessel capable of multifaceted roles. During World War II, the Aikoku Maru was converted into an armed merchant cruiser. It was outfitted with heavy guns, anti-aircraft artillery, and depth charges. Its duties were diverse, including troop transport, cargo shipment, and engaging enemy ships.
The Aikoku Maru participated in several key operations during the war. Notably, it was involved in the invasion of Malaya and the Dutch East Indies, contributing to Japan’s initial rapid advancements. The ship also played a role in transporting valuable resources such as tin and rubber, which were critical to the Japanese war effort.
Circumstances of the sinking
The Aikoku Maru met its fate on the 16th February 1944 on the first day of Operation Hailstone. Whilst anchored in the lagoon, a bomb launched by an aircraft from the aircraft carrier USS Intrepid exploded in the officer’s wardroom. This caused a huge fire. She was then hit three more times, with the third hit coming from a torpedo. This set off the ammunition stored in hold number one and created a huge explosion, which killed 945 people (730 were soldiers from the Imperial Japanese Army). The ship sank in under two minutes and only two people survived.
The wreck today
The Aikoku Maru now lies upright at a depth of 65 meters. The bow was destroyed in the explosion. The shallowest part of the wreck is the collapsed smokestack at 40m. Aft of the smokestack, the superstructure is intact and areas to explore include several cargo holds, the engine room, the auxhillary steering at the stern and the anti-aircraft gun that is still pointing up as it was on the day it sank.
Many of the human remains were removed in 1980, but some still remain, so when diving the wreck please respect that it’s a war grave.
Nippo Maru
The Nippo Maru was launched in 1922 and used as a merchant tanker. Requisitioned by the navy in World War II, the ship was converted to an auxiliary water tanker and entered service in 1941. In 1941 she ferried water and troops between Japan, South Korea, and Taiwan. From 1942 to 1944, she supported the Imperial Japanese Navy (IJN) in the Pacific.
The Sinking
On the 17th of February 1944, the Nippo Maru was attacked by three TBF Avengers from the USS Essex whilst at anchor off the Island of Dublon. She received direct hits to the engine room and cargo hold. All crew were evacuated safely.
The Wreck Today
The wreck lies upright with a list to port at a depth of approximately 45 meters (148 feet), the deck is at 30 meters (98 feet) and the shallowest point is 21m (70ft).The bow is the deepest part of the wreck.
On deck, you will find a type 97 tank (missing the turret) and three howitzers further aft. Next to the tank is the remains of a flatbed truck half hanging off the deck. Another truck lies on the seabed. There are 5 holds in total. The forward hold contains detonators, artillery shells, mines, some oil drums, and gas masks. Holds 1 and 2 have some bronze rangefinders, but little else. Holds 3 and 4 contain huge numbers of beer bottles, some radio equipment, and barrels for 5″ guns.
The Bridge
The highlight of a dive is the bridge, which is fairly intact. The helm is still standing and is a sought-after place for photographers. Below the bridge lies the officers’ quarters and the galley. Personal items of the crew are still visible.
Marine Life
Unsurprisingly, the Nippo Maru is covered in marine life- such as sponges and coral, and larger pelagics are often seen, such as eagle rays and sometimes dolphins.
Hoki Maru
Originally built in 1921 as the Hauraki by William Denny and Brothers in Scotland, the Hoki Maru served the Union Steam Ship Company of New Zealand as a general freighter. After being captured by the Japanese in 1942, it was renamed and utilised as a military supply vessel.
On 17 February 1944, during Operation Hailstone, it was bombed while carrying a volatile cargo, including aviation fuel. The resulting explosion tore the ship apart and sank it within minutes.
The wreck today
Today, the wreck lies upright at depths ranging from 15 to 50 metres. Its holds contain well-preserved artefacts such as trucks, machinery, and building materials, making it a favourite dive site in Chuuk Lagoon. Coral and sponges now cover the structure, and large schools of fish frequent the wreck.
Unkai Maru
The Unkai Maru was constructed in 1905 by the W. Gray & Company shipyard in West Hartlepool, England. Originally named Venus, the ship measured approximately 100 metres in length and had a gross tonnage of 3,121 tons. In 1911, it was sold to the Yamashita Kisen Line of Japan and renamed Unkai Maru, operating primarily as a freighter along coastal and international trade routes.
With the escalation of World War II, the Imperial Japanese Navy requisitioned the Unkai Maru for military logistics, utilising it to transport supplies and equipment to various Pacific outposts.
The wreck today
The Unkai Maru rests upright on the seabed at 40 metres. The wreck is notable for its well-preserved structure, with the bow gun still intact and the cargo holds accessible to divers. The ship’s superstructure and masts are encrusted with a variety of corals and sponges, attracting diverse marine life. The relatively shallow depth and upright position make it a popular dive site.
Hanagawa Maru
The Hanakawa Maru, a Japanese passenger and cargo vessel, was constructed in 1943 by the Kawasaki Dockyard Company in Kobe, Japan. Designed as a Standard B-type freighter, it measured approximately 112 metres in length with a gross tonnage of 4,739 tons. Prior to its wartime service, it was intended for commercial use, facilitating the transport of passengers and goods across Japanese territories.
During World War II, the Imperial Japanese Navy requisitioned the Hanakawa Maru for military operations, utilising it to transport troops and supplies to various Pacific outposts. On the morning of 17 February 1944, while offloading Japanese Army troops outside Truk Lagoon, the vessel came under attack by U.S. Navy carrier aircraft from the USS Bunker Hill and USS Monterey. The Hanakawa Maru sustained multiple torpedo hits, leading to a rapid sinking. Burning wreckage drifted to Udot Island, igniting fires in a mangrove swamp and damaging nearby structures.
The wreck today
Today, the wreck of the Hanakawa Maru rests upright on the seabed at a depth of approximately 30 metres. The ship is relatively intact, with notable features such as a short-barrel 4.7-inch anti-submarine gun mounted on the stern. The wreck is rarely dived due to its location, over an hour away by boat from the main lagoon, and the presence of residual aviation fuel that can pose hazards to divers.
Fumizuki Maru
The Fumizuki was a Mutsuki-class destroyer of the Imperial Japanese Navy, constructed at the Fujinagata Shipyards in Osaka. Laid down on 20 October 1924 and launched on 16 February 1926, she was commissioned on 3 July 1926. Initially designated as Destroyer No. 29, she was renamed Fumizuki on 1 August 1928. The vessel measured approximately 102.4 metres in length, with a beam of 9.16 metres and a standard displacement of 1,336 tons. Her armament included four 12 cm Type 3 naval guns and two triple 61 cm torpedo tubes.
During her service, Fumizuki participated in various naval operations, including escort duties and troop transport missions. Notably, she was involved in the evacuation of Japanese forces from Guadalcanal in early 1943. On 16 September 1942, she sustained heavy damage after a collision with the transport Kachidoki Maru in the Formosa Strait, necessitating repairs at Sasebo until early 1943.
In January 1943, she escorted the seaplane tender Kamikawa Maru from Sasebo via Truk and Rabaul to the Shortland Islands, and remained throughout February to cover Operation KE, the evacuation of Japanese forces from Guadalcanal. She continued to serve in the South Pacific, performing escort and transport roles.
On 4 January 1944, while near Kavieng, Papua New Guinea, Fumizuki was damaged in an air raid by U.S. aircraft. Subsequently, she returned to Truk Lagoon for repairs. During the U.S. Navy’s Operation Hailstone, Fumizuki was attacked and further damaged. Despite efforts to save the vessel, she sank in the lagoon.
The wreck today
The wreck of the Fumizuki now lies on its starboard side at a depth of approximately 35 metres in Chuuk Lagoon. The hull remains largely intact, with the main armament and torpedo tubes still visible. The superstructure has suffered damage, likely from the attacks and subsequent sinking. The wreck has become encrusted with coral and marine growth, attracting a variety of sea life, making it a notable dive site for those exploring the underwater relics of Chuuk Lagoon.
IJN I-169 Submarine
The I-169, originally designated I-69, was a Kaidai-class cruiser submarine of the KD6 sub-class, constructed for the Imperial Japanese Navy (IJN). Built by Mitsubishi at their Kobe shipyard, the submarine was laid down on 22 December 1931, launched on 15 February 1934, and commissioned on 28 September 1935. Measuring approximately 98.4 metres in length with a beam of 8.2 metres, I-169 had a surfaced displacement of 1,400 tons and a submerged displacement of 2,440 tons. Her armament included six 53.3 cm torpedo tubes with a complement of 14 torpedoes, a 100 mm deck gun, and a 13.2 mm anti-aircraft machine gun.
During World War II, I-169 participated in several significant operations. She conducted six war patrols and supported the attack on Pearl Harbor in December 1941, the Battle of Midway in June 1942, the Guadalcanal campaign, the Aleutians campaign, and the defence of the Gilbert Islands. Throughout these operations, I-169 played roles in reconnaissance, troop transport, and offensive engagements against Allied shipping.
In April 1944, while stationed at Truk Lagoon, I-169 was ordered to submerge to avoid detection during an anticipated U.S. air raid. Due to a mechanical failure, the submarine was unable to resurface, leading to the entrapment and eventual death of her crew. Rescue attempts were unsuccessful, and the last communication with the crew occurred on 7 April 1944. The submarine was officially struck from the naval register on 10 June 1944.
The wreck today
Today, the wreck of I-169 rests on the seabed of Chuuk Lagoon at a depth of approximately 40 metres. The submarine remains largely intact, with the hull and conning tower well-preserved. As a war grave, the site is treated with respect by divers, and penetration into the wreck is generally discouraged. The exterior is encrusted with coral and marine growth, attracting various sea life, which has transformed the submarine into an artificial reef.
The I-169 serves as a poignant underwater memorial, and a reminder to divers that Chuuk lagoon was a place of great suffering- easy to forget when enjoying relaxing dives in tropical water.
Amagisan Maru
The Amagisan Maru, a Japanese passenger-cargo vessel, was constructed in 1933 by Mitsui Bussan Kaisha Ltd. at their Tama shipyard in Japan. The ship measured approximately 137 metres in length, with a beam of 18.3 metres, and had a gross tonnage of 7,620 tons. Powered by a single 8,470 horsepower Mitsui Bussan (Mitsubishi) B&W six-cylinder diesel engine, the Amagisan Maru was designed for both passenger and cargo transport, operating primarily along international trade routes.
With the escalation of World War II, the Imperial Japanese Navy requisitioned the Amagisan Maru in 1943, repurposing it as a special transport vessel to support military operations across the Pacific. On 8 October 1943, while off Rabaul, the ship was attacked by a submarine and sustained damage to the No. 6 hold from a torpedo hit, causing flooding but no explosion. The vessel underwent repairs and continued its service.
On 17 February 1944, during Operation Hailstone, the Amagisan Maru was anchored in Chuuk Lagoon as part of a convoy unloading cargo. The ship came under attack by five Curtiss SB2C Helldiver dive-bombers and four Grumman TBF Avenger torpedo bombers from the USS Bunker Hill. A 1,000-pound bomb struck the bridge, killing the commander and one enlisted man, and severely wounding several others. Subsequent torpedo hits forward and aft caused catastrophic damage, igniting fuel oil and leading to the vessel sinking within 15 minutes.
The wreck today
Today, the wreck of the Amagisan Maru rests on the seabed at depths ranging from approximately 29 metres at the deck to 58 metres at the sand bottom. The ship lies with a significant port list of at least 45 degrees. The bow area is shallower, with the deck at 29 metres and the sand at 42 metres, while the stern is deeper, with the deck at 52 metres and the sand at 58 metres.
The wreck is largely intact, with notable features including a large bow gun and accessible cargo holds containing trucks, aircraft parts, and fuel drums. The superstructure is encrusted with coral and marine growth, attracting diverse sea life. The Amagisan Maru is a popular dive site in Chuuk Lagoon.
Shotan Maru
The Shotan Maru, a Japanese cargo vessel, was constructed in 1943 by the Mitsui Shipbuilding & Engineering Company in Tamano, Japan. Designed as a Standard 1D wartime freighter, the ship measured approximately 87 metres in length and had a gross tonnage of 1,999 tons. Primarily intended for logistical support, the Shotan Maru was utilised to transport military supplies and equipment across the Pacific theatre during World War II.
On 17 February 1944, during Operation Hailstone, the Shotan Maru was underway in Chuuk Lagoon when it came under attack by U.S. Navy aircraft. The vessel sustained a direct hit from a bomb in the aft hold, leading to a massive explosion that caused the ship to sink rapidly. The exact number of casualties remains uncertain, but it is believed that a significant portion of the crew perished in the attack.
The wreck today
Today, the wreck of the Shotan Maru lies upright on the seabed of Chuuk Lagoon at depths ranging from approximately 36 to 50 metres. The ship’s structure is relatively intact, with the stern gun still in place and much of the railing preserved. The forward holds contain remnants of trucks and a large mobile compressor, though these artefacts are in a deteriorated state.
Seiko Maru
The Seiko Maru, a Japanese cargo vessel, was constructed in 1940 by the Uraga Dock Company in Uraga, Japan. Designed as a passenger-cargo ship, it measured approximately 119 metres in length, with a beam of 16 metres, and had a gross tonnage of 5,385 tons. Prior to World War II, the Seiko Maru operated under the ownership of the Seiko Kisen Line, facilitating the transport of goods and passengers across Japanese coastal and international routes.
With the advent of World War II, the Imperial Japanese Navy requisitioned the Seiko Maru for military logistics, utilising it to transport essential supplies, including fuel and ammunition, to various Pacific outposts. On 31 July 1943, the vessel sustained damage from a torpedo attack by the USS Pogy (SS-266) but managed to reach port for repairs.
On 17 February 1944, during Operation Hailstone, the Seiko Maru was anchored in Chuuk Lagoon. U.S. Navy SBD Dauntless dive bombers from the USS Enterprise targeted the vessel, scoring direct hits on both sides and the stern. A large explosion ensued, causing the ship to sink immediately.
The wreck today
Today, the wreck of the Seiko Maru rests upright on the seabed of Chuuk Lagoon at around 49 metres. The ship’s structure is relatively intact, with the deck and superstructure encrusted with coral and marine growth.
Divers can explore the cargo holds, which contain remnants of wartime supplies, including fuel drums and machinery parts. The engine room and bridge are accessible, offering insights into the ship’s operational areas.
Kiyosumi Maru
The Kiyosumi Maru, a Japanese passenger-cargo vessel, was constructed in 1934 by Kawasaki Dockyard Co., Ltd., in Kobe, Japan. Measuring approximately 140 metres in length with a gross tonnage of 8,614 tons, the ship was initially operated by Kokusai Kisen Kabushiki Kaisha (K-Line) and served commercial routes, including voyages to New York.
In November 1941, the Imperial Japanese Navy requisitioned the Kiyosumi Maru, converting it into an armed merchant cruiser. The retrofit included the installation of eight 6-inch (152.4 mm) guns, two twin torpedo tubes, and anti-aircraft weaponry. The vessel participated in various wartime operations, including serving as a troop carrier during the Battle of Midway in June 1942. On 1 January 1944, while en route from Kavieng to Truk, the Kiyosumi Maru was heavily damaged by a submarine attack, necessitating repairs upon arrival.
On 17 February 1944, during Operation Hailstone, U.S. Navy aircraft launched a massive assault on Japanese forces in Chuuk Lagoon. The Kiyosumi Maru sustained multiple bomb hits, leading to severe damage and eventual sinking.
The wreck today
Today, the wreck of the Kiyosumi Maru lies on its port side on the seabed of Chuuk Lagoon, with depths ranging from approximately 15 to 30 metres. The ship’s structure is relatively intact, with accessible cargo holds containing remnants of military supplies and vehicles. The superstructure is encrusted with coral and marine growth, attracting diverse sea life. The wreck’s relatively shallow depth and preserved state make it a popular dive site.
Shinkoku Maru
The Shinkoku Maru, a significant wreck in Chuuk Lagoon, was constructed in 1939 by the Kawasaki Dockyard Company in Kobe, Japan. Designed as a 10,020-ton fleet oiler, it measured approximately 152 metres in length and 19 metres in beam, serving the Imperial Japanese Navy by providing essential fuel supplies to naval vessels.
During World War II, the Shinkoku Maru played a crucial logistical role, notably participating in the attack on Pearl Harbor in December 1941. Throughout the war, it continued to support Japanese naval operations across the Pacific by refuelling warships at sea.
On 17 February 1944, as part of Operation Hailstone, U.S. carrier-based aircraft launched a massive assault on the Japanese fleet anchored in Chuuk Lagoon. The Shinkoku Maru sustained multiple attacks, including bomb and torpedo strikes, leading to its sinking.
The wreck today
Today, the Shinkoku Maru rests upright on the seabed of Chuuk Lagoon at depths ranging from approximately 12 metres at the bridge to 40 metres at the main deck. The wreck is renowned for its excellent preservation and vibrant marine life, with extensive coral and sponge growth adorning its structure.
Divers can explore various sections, including the bridge, engine room, and medical bay, where artefacts such as medical supplies remain visible. The relatively shallow depth and upright position make it accessible to divers of varying experience levels, contributing to its status as one of the most celebrated wrecks in Chuuk Lagoon.
Gosei Maru
The Gosei Maru was constructed in 1937 by the Tsurumi Iron Works Dockyard in Japan. Designed as a coastal freighter, it measured approximately 80 metres in length and had a gross tonnage of 1,931 tons. Prior to World War II, the Gosei Maru operated under the Koun Kisen Line, facilitating the transport of goods along Japan’s coastal routes.
With the onset of World War II, the Imperial Japanese Navy requisitioned the Gosei Maru in 1941, repurposing it as a supply ship for the Sixth Fleet submarines. In this capacity, it transported essential military supplies, including torpedoes and depth charges, to support naval operations across the Pacific.
On 17 February 1944, the Gosei Maru was anchored off Uman Island. The vessel sustained a direct hit from an aerial torpedo in the forward hold, which destroyed much of the bridge and superstructure, causing the ship to sink.
The wreck today
Today, the Gosei Maru lies on its port side along a sloping seabed in Chuuk Lagoon, with depths ranging from approximately 6 metres at the stern to 34 metres at the bow. The shallow stern section, with its exposed rudder and propeller, is easily accessible and offers excellent photographic opportunities.
The forward holds contain remnants of its wartime cargo, including torpedoes, though many were destroyed in 1976 to eliminate the risk of detonation. The wreck is encrusted with coral and serves as a habitat for diverse marine life, making it a compelling site for divers exploring the historical underwater landscape of Chuuk Lagoon.
Momokawa Maru
The Momokawa Maru, a Japanese cargo vessel, was constructed in 1940 by Kawasaki Dockyard Co., Ltd., in Kobe, Japan. Designed primarily for timber transport, the ship measured approximately 107 metres in length with a gross tonnage of 3,829 tons. Prior to World War II, the Momokawa Maru operated under civilian service, transporting lumber from Siberia to Japan.
In late 1943, the Imperial Japanese Navy requisitioned the Momokawa Maru for military purposes, utilising it as a bulk cargo carrier to support wartime logistics. On 17 February 1944, during Operation Hailstone, U.S. carrier-based aircraft launched a massive assault on Japanese forces in Chuuk Lagoon. The Momokawa Maru was bombed by aircraft from the USS Bunker Hill, resulting in a significant explosion that caused the vessel to sink.
The wreck today
Today, the wreck of the Momokawa Maru lies on its port side at a depth of approximately 43 metres. The ship’s structure is relatively intact, with notable features including the most intact bridge house among the wrecks in the lagoon. The cargo holds contain remnants of wartime materials, such as aircraft parts and truck frames.
IJN Oite
The IJN Oite was a Kamikaze-class destroyer of the Imperial Japanese Navy, constructed at the Uraga Dock Company in Uraga, Japan. Laid down on 16 March 1923 and launched on 27 November 1924, she was commissioned on 30 October 1925. The vessel measured approximately 98 metres in length, with a beam of 9.1 metres and a standard displacement of 1,422 tons. Her armament included four 12 cm Type 3 naval guns and three twin 53.3 cm torpedo tubes.
During her service, Oite participated in various naval operations, including escort duties and troop transport missions. She was notably involved in the invasion of Wake Island in December 1941 and the occupation of New Guinea and the Solomon Islands in early 1942. Throughout the war, Oite continued to serve in the South Pacific, performing critical escort and transport roles.
On 15 February 1944, Oite departed Truk Lagoon, escorting the light cruiser Agano. The following day, Agano was torpedoed and sunk by the U.S. submarine Skate. Oite rescued approximately 523 survivors and returned to Truk Lagoon. On 17 February 1944, during Operation Hailstone, Oite came under attack by U.S. aircraft. A torpedo strike caused a massive explosion, sinking the vessel rapidly. Tragically, nearly all aboard perished, including the survivors rescued from Agano.
The wreck today
The wreck of Oite was discovered on 1 March 1986 by Blue Lagoon dive operator Gradvin Aisek and researcher Tomoyuki Yoshimura. It rests upright on the seabed of Chuuk Lagoon at depths ranging from approximately 50 to 64 metres. The ship’s structure is relatively intact, with notable features such as the forward gun and torpedo tubes still visible.
The Rio de Janeiro Maru, a Japanese passenger-cargo liner, was constructed in 1930 by Mitsubishi Shipbuilding & Engineering Co. at their Nagasaki Shipyard. Measuring approximately 140 metres in length with a gross tonnage of 9,626 tons, the vessel was operated by Osaka Shosen Kaisha (OSK) Line. It primarily served routes between Japan and South America, accommodating up to 1,140 passengers across eight decks.
In 1940, amid escalating military tensions, the Imperial Japanese Navy requisitioned the Rio de Janeiro Maru, converting it into a submarine tender. This role involved providing maintenance, supplies, and support to submarine fleets operating in the Pacific theatre. The vessel was later reclassified as a transport ship in 1943, tasked with moving troops and equipment to various operational areas.
During Operation Hailstone, the Rio de Janeiro Maru was anchored east of Uman Island. It was struck by 1,000-pound bombs in one of the initial attacks. The damage inflicted caused the ship to sink shortly after midnight on 18 February.
The wreck today
Today, the wreck of the Rio de Janeiro Maru rests on its starboard side at a depth of approximately 35 metres. The vessel’s structure remains relatively intact, with notable features such as a large bow gun and expansive cargo holds accessible to divers.
The Heian Maru, a Japanese passenger-cargo liner, was constructed in 1930 by the Osaka Iron Works for the Nippon Yusen Kaisha (NYK) shipping company. Measuring approximately 155 metres in length with a gross tonnage of 11,616 tons, it was one of three sister ships designed for trans-Pacific service between Yokohama and Seattle. The vessel was renowned for its speed and comfort, reflecting Japan’s growing maritime capabilities during that era.
In August 1941, as tensions escalated leading up to World War II, the Imperial Japanese Navy requisitioned the Heian Maru and converted it into a submarine tender for the 6th Submarine Fleet. This conversion involved outfitting the ship with repair facilities, supply storage, and accommodations to support submarine operations across the Pacific theatre. The Heian Maru played a crucial role in maintaining the operational readiness of Japan’s submarine forces during the early years of the war.
On 17 February 1944, the Heian Maru was subjected to multiple bomb and torpedo attacks, resulting in severe damage, which eventually cause the vessel to sink.
The wreck today
Today, the wreck of the Heian Maru rests on its port side at depths ranging from approximately 10 to 35 metres. As the largest shipwreck in the lagoon, it offers divers extensive areas to explore, including the bridge, engine room, and cargo holds. Notably, the holds contain artifacts such as torpedoes, periscopes, and other submarine-related equipment, reflecting its role as a submarine tender.
The Kensho Maru was a Japanese passenger-cargo vessel constructed in 1938 by Mitsubishi Heavy Industries at their Nagasaki shipyard. Measuring approximately 86.9 metres in length with a gross tonnage of 4,862 tons, the ship was operated by the Yamashita Kisen Line. Primarily serving commercial routes, the Kensho Maru transported passengers and goods between Japan and its overseas territories.
In 1941, as Japan expanded its military operations, the Imperial Japanese Navy requisitioned the Kensho Maru for wartime service. The vessel was repurposed to transport military supplies and personnel to various Pacific outposts, playing a crucial role in sustaining Japan’s logistical efforts during the war.
On 17 February 1944, during Operation Hailstone, the Kensho Maru was anchored in Chuuk Lagoon, serving as a repair ship. U.S. Navy aircraft targeted the vessel, causing severe damage from multiple aerial bomb strikes. The attacks led to its sinking, contributing to the significant losses Japan experienced during the operation.
The wreck today
Today, the wreck of the Kensho Maru rests upright on the seabed of Chuuk Lagoon at depths ranging from approximately 12 to 40 metres. The ship’s structure is relatively intact, with the engine room and cargo holds accessible to divers. Artifacts such as machinery parts and medical supplies can still be found within the holds, offering insights into the vessel’s operational history.
The Fujisan Maru was a Japanese oil tanker constructed in 1931 by the Harima Shipbuilding & Engineering Company in Aioi, Japan. Measuring approximately 150 metres in length with a gross tonnage of 9,524 tons, the vessel was operated by the Nippon Tanker Shipping Company. Primarily designed for the transportation of crude oil, the Fujisan Maru played a significant role in Japan’s maritime oil logistics during the pre-war period.
With the onset of World War II, the Imperial Japanese Navy requisitioned the Fujisan Maru in late 1941, repurposing it as a fleet oiler to support naval operations across the Pacific theatre. The vessel participated in various military campaigns, including the Battle of Midway in June 1942, where it served as part of the Aleutian diversionary task group. Due to its speed and capacity, the Fujisan Maru was also involved in the “Tokyo Express,” transporting troops and supplies to reinforce Japanese positions in the Pacific. In December 1943, the ship was damaged by a bomb from a B-17 aircraft but was repaired and returned to service by early 1944.
On 17 February 1944, during Operation Hailstone, the Fujisan Maru was underway in Chuuk Lagoon when it came under attack by U.S. Navy aircraft. The vessel was struck by 1,000-pound delayed-action armour-piercing bombs, resulting in catastrophic damage that led to its sinking.
The wreck today
Today, the wreck of the Fujisan Maru rests upright on the seabed of Chuuk Lagoon at depths ranging from approximately 37 metres at the superstructure to 60 metres at the sand bottom. The ship’s structure remains relatively intact, with notable features including the engine order telegraph still signaling “full ahead,” and machine guns with scattered ammunition, indicating the crew’s futile defence efforts.
The Nagano Maru was a Japanese passenger-cargo vessel constructed in 1917 by the Kawasaki Dockyard Company in Kobe, Japan. Measuring approximately 105 metres in length with a gross tonnage of 3,824 tons, the ship was operated by the Nippon Yusen Kaisha (NYK) Line. It primarily served commercial routes, facilitating the transport of passengers and goods between Japan and its overseas territories.
In the early stages of World War II, the Imperial Japanese Navy requisitioned the Nagano Maru for military service, repurposing it to transport troops, equipment, and supplies to various operational areas across the Pacific. The vessel played a role in sustaining Japan’s wartime logistics, contributing to the movement of essential resources.
On 17 February 1944, during Operation Hailstone, the Nagano Maru was anchored in Chuuk Lagoon. U.S. Navy aircraft targeted the vessel, resulting in significant damage from aerial bombing and it’s eventual sinking.
The wreck today
Today, the wreck of the Nagano Maru rests upright on the seabed of Chuuk Lagoon at depths ranging from approximately 43 to 64 metres. The ship’s structure remains relatively intact, with accessible cargo holds containing remnants of wartime materials, such as vehicles and machinery parts.
The Yamagiri Maru was a Japanese passenger-cargo vessel constructed in 1938 by Mitsubishi Heavy Industries at their Nagasaki shipyard. Measuring approximately 134 meters in length with a gross tonnage of 6,438 tons, the ship was operated by the Yamashita Kisen Line. Prior to World War II, the Yamagiri Maru facilitated the transport of passengers and goods between Japan and its overseas territories.
In September 1941, as Japan expanded its military operations, the Imperial Japanese Navy requisitioned the Yamagiri Maru for wartime service. The vessel was repurposed to transport military supplies and personnel to various Pacific outposts, playing a crucial role in sustaining Japan’s wartime logistics. On 28 August 1943, while part of a convoy west of Mussau Island in the Admiralties, the Yamagiri Maru was torpedoed by the USS Drum (SS-228), sustaining significant damage that necessitated repairs.
On 17 February 1944, during Operation Hailstone, the Yamagiri Maru was anchored in Chuuk Lagoon. U.S. Navy SBD Dauntless dive bombers from the aircraft carriers USS Yorktown (CV-10) and USS Bunker Hill (CV-17) targeted the vessel, releasing bombs from an altitude of approximately 150 meters. The ship sustained direct hits, with one bomb striking the aft section near the engine room, causing a massive explosion. The damage was catastrophic, and the Yamagiri Maru sank rapidly, reportedly within minutes.
The wreck today
Today, the wreck of the Yamagiri Maru rests on its port side at depths ranging from approximately 15 to 34 meters. The ship’s structure remains relatively intact, with accessible cargo holds containing 18-inch diameter artillery shells intended for battleships, including the Musashi. The engine room and bridge are also accessible, offering insights into the ship’s operational areas.
The Hoyo Maru was a Japanese oil tanker constructed in 1936 by the Harima Shipbuilding & Engineering Company in Aioi, Japan. Measuring approximately 150 meters in length with a gross tonnage of 8,691 tons, the vessel was operated by the Nippon Tanker Shipping Company. Primarily designed for the transportation of crude oil, the Hoyo Maru played a significant role in Japan’s maritime oil logistics during the pre-war period.
In 1941, as Japan expanded its military operations, the Imperial Japanese Navy requisitioned the Hoyo Maru for wartime service. The vessel was repurposed as a fleet oiler, providing essential fuel supplies to naval ships operating across the Pacific theater. The Hoyo Maru participated in various military campaigns, including Operation MO during April-May 1942.
On 6 November 1943, the Hoyo Maru was torpedoed by the USS Haddock (SS-231) near Chuuk Lagoon, sustaining significant damage and resulting in fires aboard that led to the deaths of two crew members. The vessel was towed to Chuuk Lagoon for repairs.
On 17 February 1944, during Operation Hailstone, the Hoyo Maru was strafed and dive-bombed by SBD Dauntless dive bombers from the USS Enterprise (CV-6) and TBF Avenger torpedo bombers from the USS Yorktown (CV-10). Bomb hits caused the already damaged ship to capsize and sink. Six crew members aboard were killed during the attack.
The wreck today
The wreck of the Hoyo Maru now lies upright at depths ranging from 15 to 35 metres. Divers exploring the wreck can observe remnants of its wartime cargo, including spare parts, machinery, and oil barrels scattered around the holds and seabed. The superstructure, although damaged, remains partially intact and accessible to experienced divers.
The Kikukawa Maru was a Japanese cargo-passenger vessel constructed in December 1938 by Kawasaki Heavy Industries at their Kobe shipyard. Measuring approximately 108.1 meters in length and 15.2 meters in width, with a displacement of 3,833 tons, the ship was operated by Kawasaki Kisen Kaisha. It primarily served commercial routes, facilitating the transport of passengers and goods between Japan and its overseas territories.
In the early stages of World War II, the Imperial Japanese Navy requisitioned the Kikukawa Maru for military service. The vessel was repurposed to transport troops, equipment, and supplies to various operational areas across the Pacific, playing a crucial role in sustaining Japan’s wartime logistics.
On 7 October 1943, while anchored northeast of Eten Island in Chuuk Lagoon, the Kikukawa Maru was unloading a cargo primarily consisting of ammunition and possibly fuel drums. A fire broke out aboard the vessel, prompting firefighting efforts, including assistance from the firefighting boat Ojima, which tied up alongside. As the fire reached the cargo of fuel and ammunition, a massive explosion ensued, resulting in the rapid sinking of both the Kikukawa Maru and the Ojima.
The explosion was so powerful that it obliterated the rear third of the Kikukawa Maru and caused the disappearance of several other craft involved in the unloading process. Tragically, five crew members and 39 passengers aboard the Kikukawa Maru lost their lives in the incident.
The wreck today
Today, the wreck of the Kikukawa Maru rests on the seabed of Chuuk Lagoon at a depth of approximately 36.5 meters (120 feet). The front half of the ship lies on an underwater hill, while the aft section was destroyed in the explosion. Inside the forward hull, divers can find oil drums, a compressor, and other equipment. Aircraft parts, including bodies, propellers, engines, and wheels, are scattered on the ocean floor around the wreck, along with a truck amidst the debris.
The Sankisan Maru was a Japanese cargo vessel constructed in 1943 by the Kawasaki Dockyard Company in Kobe, Japan. Measuring approximately 112 meters in length with a gross tonnage of 4,776 tons, the ship was operated by the Yamashita Kisen Line. Primarily designed for the transportation of military supplies, the Sankisan Maru played a significant role in Japan’s wartime logistics during World War II.
On 17 February 1944, during Operation Hailstone, the Sankisan Maru was anchored near Uman Island in Chuuk Lagoon. U.S. Navy aircraft launched a series of attacks on Japanese vessels in the lagoon. The Sankisan Maru sustained a direct hit from a bomb in its aft hold, which contained ammunition. The resulting explosion destroyed the bridge to the stern section of the ship, causing it to sink. The forward part of the vessel remained relatively intact.
The wreck today
Today, the wreck of the Sankisan Maru rests upright on the seabed of Chuuk Lagoon at depths ranging from approximately 3 to 48 meters. The forward holds contain various artifacts, including aircraft parts such as engines and wings, boxes of ammunition, and medicine bottles. Trucks and other vehicles are also present on the deck. The masts extend close to the surface and are adorned with vibrant coral formations, attracting a diverse array of marine life.
The Yubae Maru was a Japanese cargo vessel constructed in 1939 by the Kawasaki Dockyard Company in Kobe, Japan. Measuring approximately 93 meters in length with a gross tonnage of 3,217 tons, the ship was operated by the Nippon Yusen Kaisha (NYK) Line. Primarily designed for the transportation of goods, the Yubae Maru played a role in Japan’s maritime logistics during World War II.
During Operation Hailstone, the Yubae Maru sustained significant damage from aerial bombing, leading to its sinking. Specific details regarding the exact location of the damage and the time it took for the vessel to sink are not well-documented.
The wreck today
Today, the wreck of the Yubae Maru rests upright on the seabed at depths ranging from 24 to 35 meters. The ship’s structure remains relatively intact, with accessible cargo holds containing remnants of wartime materials.
Katsuragisan Maru
The Katsuragisan Maru was a Japanese cargo ship built in 1925 for Mitsui Bussan K.K. The vessel had a gross registered tonnage of 2,427 tons and was primarily used for commercial purposes before being requisitioned by the Imperial Japanese Navy during World War II for use as a transport ship.
In February 1944, the Katsuragisan Maru arrived at Truk Atoll (now known as Chuuk Lagoon) carrying a cargo of war supplies. Unbeknownst to the ship’s captain, the Japanese had closed off the Northeast Pass of the lagoon and laid friendly mines to protect against Allied attacks. As the Katsuragisan Maru entered the lagoon through this pass, it struck one of these mines, resulting in significant damage that led to the vessel’s sinking.
The wreck today
The wreck of the Katsuragisan Maru rests upright on the seabed on the outer edges of Chuuk Lagoon, with depths ranging from 51 to 68 meters. The depth makes it one of the deeper wrecks in the lagoon, often attracting technical divers. The vessel’s superstructure has collapsed, but notable features such as the stern gun remain visible, providing a glimpse into its wartime role. Due to its location near the lagoon’s northeastern pass, strong currents are common, and the site is less frequently visited compared to shallower wrecks in the area.
The Reiyo Maru was a Japanese passenger-cargo vessel constructed in 1920, measuring approximately 121 meters in length with a gross tonnage of 5,446 tons. Operated by the Toyo Kisen Kaisha (TKK) Line, it primarily facilitated the transport of passengers and goods between Japan and its overseas territories.
In the early stages of World War II, the Imperial Japanese Navy requisitioned the Reiyo Maru for military service, repurposing it to transport troops, equipment, and supplies across the Pacific. The vessel played a significant role in sustaining Japan’s wartime logistics.
On 16 February 1944, U.S. Navy aircraft launched attacks, with two 1,000-pound bombs striking the vessel, causing catastrophic damage. The ship remained afloat for two days before sinking on 19 February 1944 at the 4th Fleet anchorage, approximately three miles off Eten Island.
The wreck today
Today, the wreck of the Reiyo Maru rests upright on the seabed of Chuuk Lagoon, with depths ranging from 53 meters at the shallowest point to 67 meters at the deepest. The ship’s structure remains relatively intact.
The Mitsubishi G4M Betty bomber was a twin-engine, land-based aircraft used extensively by the Imperial Japanese Navy during World War II. It was designed for long-range bombing missions and maritime operations. Despite its speed and range, the Betty bomber’s design compromised crew safety, as it lacked self-sealing fuel tanks and adequate armour. This vulnerability led to its reputation as the “flying cigar” among Allied forces due to its tendency to catch fire when hit.
The Betty bomber in Chuuk Lagoon is believed to have crashed during World War II, although the exact circumstances of its loss remain unclear. Some accounts suggest it crashed during takeoff or landing due to mechanical failure or pilot error. Other theories propose that it was damaged during Operation Hailstone and forced to ditch into the lagoon. Limited historical records make it difficult to confirm the precise details of the incident.
The wreck today
Today, the wreck of the Betty bomber rests upright on the seabed at a depth of 15 to 18 metres. The fuselage is largely intact, though the tail section is detached and lies nearby. The cockpit area retains remnants of the pilot’s seat and instrument panels, offering divers a glimpse into the aircraft’s operational features. The wings are still in place, with one propeller blade bent, likely indicating the force of the crash. The engines are on the seabed a shot swim away, and other items lie scattered on the sea bed, including a radio, machine guns, and even a toilet.
The Kawanishi H8K, known to Allied forces as the “Emily,” was a four-engine flying boat utilised by the Imperial Japanese Navy during World War II. Renowned for its long-range capabilities and substantial defensive armament, the H8K was considered one of the most advanced flying boats of its time. It was primarily employed for maritime patrols, reconnaissance missions, and transport duties across the Pacific theatre.
In the context of Chuuk Lagoon, a significant Japanese naval base during the war, an H8K Emily flying boat met its demise under circumstances that remain somewhat unclear. Some accounts suggest that the aircraft was destroyed during an Allied air raid, while others propose it was scuttled by Japanese forces to prevent capture. The exact details of its sinking are not well-documented.
The wreck today
Today, the wreck of the Emily flying boat rests on the seabed at 15 meters. The aircraft lies inverted, with its wings and fuselage largely intact. The hull shows signs of damage consistent with explosive impact, and the interior compartments are accessible to divers. Over time, the wreck has become encrusted with coral and marine growth, transforming into an artificial reef that supports a variety of marine life. The relatively shallow depth and good visibility make the Emily flying boat wreck a popular dive site. It’s definitely not a tech dive.
Please contact me if you have updated information on the condition of the wrecks.
