In the hold of the Fujikawa Maru, at a depth of around 34 metres in the western Pacific, there are aircraft engines.
They are Mitsubishi Zeros. Or rather, the engines of Mitsubishi Zeros; stacked in the cargo hold precisely as Japanese engineers left them in February 1944. Coral has grown over everything. Fish swim through the space where workers once walked. The light that reaches this far down is not quite darkness and not quite light. The engines sit in it, patient and perfectly preserved, waiting for an assembly that is never going to happen.
This is Chuuk Lagoon. And there are fifty more ships like the Fujikawa Maru down there.
Operation Hailstone
In February 1944, the Japanese Fourth Fleet was based at Truk — the name by which Chuuk was then commonly known — a heavily fortified natural harbour in the Caroline Islands of the western Pacific. Truk was Japan’s most important naval base in the region, its “Gibraltar of the Pacific,” and the Allies had largely avoided engaging it directly. In early 1944, that changed.
On 17 and 18 February 1944, American carrier aircraft launched a sustained assault on the base in an operation called Hailstone. In 48 hours, they sank at least 40 ships and destroyed between 250 and 270 aircraft. It was one of the most decisive naval engagements of the Pacific war. Japan never used Truk as a major base again.
What the attack actually caught is worth understanding. Japanese intelligence had received warning of the raid roughly a week beforehand, and the Imperial Navy’s most valuable assets, its heavy cruisers, battleships, and aircraft carriers, were withdrawn to Palau before the American planes arrived. What remained in the lagoon when Hailstone began was predominantly the support fleet: tankers, cargo ships, supply vessels, and a handful of smaller warships. The Americans sank a functioning logistics base rather than a battle fleet. This matters because it explains what lies on the lagoon floor today. The wrecks of Chuuk are not the dramatic warships of popular imagination. They are the working vessels of a military operation — the ships that carried fuel, food, ammunition, aircraft parts, and the thousand other things an army needs to fight.
To me, that makes them more interesting, not less.
The Japanese government did not publicly acknowledge the scale of the defeat for years. The ships and the men on them simply vanished into official silence.
But they did not vanish from the lagoon.
What Lies There
The fleet that sank at Truk includes warships, tankers, cargo vessels, and supply ships. Between them, they carried the equipment of a functioning military base — and that equipment is still there.
The Sankisan Maru holds trucks and aircraft parts. The Nippo Maru carried a field gun, a tank, gas masks, and ammunition. The Fujikawa Maru has its aircraft engines and a hold full of fighter fuselages. The Shinkoku Maru was a tanker, but its most striking feature is the ship’s operating room, still almost entirely intact: instruments on the table, bottles on the shelves, coral threading slowly through everything.
Some wrecks have sake bottles. Some have personal effects — boots, mess tins, identity documents drifting loose from their original contexts over the decades, settling somewhere new.
Some have human remains.
Chuuk is not simply a dive site: it’s a graveyard.
The War Grave Question
Japanese casualties during Operation Hailstone are believed to be at least 4,500. Many of them went down with their ships. Many were never recovered and are still in the lagoon.
The wrecks of Chuuk are, by any reasonable definition, war graves. Japan has conducted retrieval expeditions over the decades and recovered some remains, but many sailors are still entombed in the ships where they died. This is known. The dive operators who run trips to the lagoon know it. The recreational divers who descend into the holds know it.
And they go anyway. This is the ethical fault line at the centre of Chuuk’s existence as a tourist destination.
Wreck tourism generates the majority of Chuuk’s income from overseas visitors. The lagoon is the main reason the islands appear on the radar of travellers at all — Chuuk is one of the poorest states in Micronesia, and the alternative to tourism revenue is its absence. The wrecks are not going anywhere. The remains are not going to be fully recovered. The question of whether recreational diving through a war grave is acceptable, or whether it can be made acceptable with sufficient reverence, has no clean answer. Different divers, different operators, and different governments have reached different conclusions.
Japan has asked, over the years, that certain wrecks be treated with greater care. The requests have been noted and incompletely observed.
What It Looks Like
The visibility in Chuuk Lagoon, on a good day, is incredible. The water is warm. The coral growth on the wrecks is dense and colourful; eighty years of marine life have turned rusting steel into something else entirely, something that no longer looks like the thing it was. A gun turret disappears under brain coral. A mast becomes a vertical reef. Fish move through engine rooms and ammunition bays with the indifference that living things show to the categories of the dead.
The Shinkoku Maru’s operating room is the image that most divers take away from Chuuk. The surgical instruments are still on the table, not because anyone arranged them for effect, but because nobody moved them. They have been there since February 1944. The coral grows around them slowly, the way it grows around everything, without regard for what it is covering.
This is not a museum. Nobody curated this. Nobody decided what to preserve or how to frame it. The fleet is simply there, becoming something other than what it was, at a pace too slow for any individual to perceive.
After the War
Chuuk after 1944 was a bypassed island. The American strategy of island-hopping left it isolated and under blockade for the remainder of the war, its garrison slowly starving. When the surrender came, the survivors were repatriated. The islands were administered first by the United States and later became part of the Federated States of Micronesia. The wrecks were left where they lay.
For decades, almost nobody outside the region knew the lagoon existed. Jacques Cousteau filmed there in 1969, and the footage reached audiences who had no idea what they were looking at. After that, slowly, the divers came.
What they found was unlike anything else on earth. Not a single wreck, isolated and studied. A fleet. An entire operational base, sunk in place, preserved by cold and depth and the particular chemistry of tropical saltwater, waiting in the dark for anyone willing to descend far enough to see it.
The Fujikawa Maru’s aircraft engines may still be there, but the assembly instructions, if there were any, are long gone. The Zeros were never built. The war they were meant to fight is over.
But he engines wait in the dark anyway.