Swimming amid the shipwrecks of Micronesia's Chuuk Lagoon is like diving into a time machine.
A ghost fleet of ships and aircraft, once part of a formidable Japanese naval base, dot the floor of the state of Chuuk's shallow waters.
They lie amid an abundance of coral and sea life, creating a spectacular underwater realm for the tourists willing to travel the vast distance to see it.
However, Chuuk's major tourism attraction is also a threat to its survival.
Toxic oil is leaking from the rusted vessels.
Experts have long feared the impacts of climate change are accelerating the ships' deterioration as warmer water temperatures and wave action from extreme weather corrode their outer shells.
Fears intensified last month when oil from an old transport ship reached the shoreline of nearby villages, turning mangroves black and prompting a state of emergency.
And the problem is only just beginning.
World's biggest shipwreck graveyard
Ranger Walter, the historic preservation officer in the state of Chuuk, swims among the wrecks often.
"When I started diving, I became addicted. It's like another world," he said.
His job is to ensure the relics and artefacts within remain undisturbed.
"We keep inventory to make sure tourists don't pick up old guns and things like that," he said.
"There's lots of rifles, handguns … even bones and human remains."
More than 4,000 Japanese soldiers perished when Chuuk Lagoon, known as "Truk" at the time, was bombarded by US forces at the tail-end of World War II.
More than 60 vessels were sunk, along with hundreds of planes which were shot out of the sky, in an attack described as "revenge for Pearl Harbor".
Before that, the base had been the centre of Japan's logistics operations in the central Pacific.
But by 1944 it was cut off from retreating Japanese forces, battlefield historian Mat McLachlan said, making the ships in the harbour sitting ducks for allied bombers.
"As the war went on the Japanese were pushed back further and further and Chuuk is a perfect example of a base that became an albatross," he said.
Today, Chuuk Lagoon is home to one of the highest concentrations of World War II shipwrecks in the world, making it a bucket-list destination for scuba divers from all over.
Chuuk division chief of commerce and industry Peter Aten said the shipwrecks were the main driver of tourism for Micronesia.
"Eighty per cent of our tourists come here because of them," he said.
A ticking time bomb
However, problems became apparent in the early 2000s when local fishermen began finding traces of oil on the surface of the lagoon.
Soon after, oil washed up onshore after a strong storm, sparking an international call for aid from the country's then-leader Manny Mori, who labelled the wrecks a "ticking time bomb".
Help came via Japan's Mine Action Service, which according to a recent report has extracted 60,000 litres of oil from the lagoon since beginning operations in 2017.
But it only scratches the surface of the overall threat, with recent estimates suggesting up to 22 million litres could still be contained with the vessels.
"What's happening right now with global warming is the rate of deterioration of our shipwrecks has sped up and started to erode much quicker than anticipated," Mr Aten said.
In February, the Australian government funded an extensive study of the wrecks at the request of Micronesia's government.
Maritime archaeologist Matt Carter led the study, which assessed 20 of the most high-risk wrecks with 3D modelling software.
"Some were sunk upright, some were blown in half, some are upside down and that all plays into how they will deteriorate," he said.
"If a wreck for example is on its side, all the forces are vertical, and it's not built to withstand those forces."
The study determined 15 of the wrecks would need to be cleaned within five to 10 years to prevent a potential large-scale spill.
But in September, just a few months after the study was submitted, disaster struck when one of the vessels assessed in the study, the Rio de Janeiro Maru, sprung a leak which left a layer of oil 10 centimetres thick on the shoreline of a nearby village.
"Fortunately, the affected villages use rainwater so there is no contamination of their local water, but there's been reported cases of dizziness due to the fumes and smell of the oil," Mr Aten said.
A state of emergency was declared, with Micronesian President Wesley Simina raising the matter during his address at the UN General Assembly in New York last month, saying the scale of the problem far exceeds Micronesia's capacity to address the issue alone.
However, getting help is not so simple.
A legal grey area
According to Mr Carter, removing oil from shipwrecks and disposing of it safely takes place often in other areas of the world, but at a steep price.
He said cleaning up a single wreck in Chuuk could cost upwards of $US10 million ($15.4 million).
"The challenge in places like Chuuk, Solomon Islands and Marshall Islands is the sheer distances involved for getting the equipment there," he said.
"The cost is significantly higher."
There is also no legal obligation for the countries responsible for putting the wrecks there in the first place to assist, according to Donald Rothwell, a maritime expert and professor of international law at the Australian National University.
He said because Micronesia was not an independent state in WWII, the legal responsibility of the wrecks fell into a grey legal area.
The peace treaties concluded at the end of the war also failed to address potential issues caused by shipwrecks or pollution.
"There's a growing awareness that this is a problem mainly affecting small island states and there is a political movement to reach a global settlement. But unfortunately that will take some time," Professor Rothwell said.
In the meantime, leaders on Chuuk have applied to have the wrecks placed on the UNESCO World Heritage List to build their profile and shed further light on the issue.
"It's obvious that this is just the beginning," Mr Aten said.
"We have 63 shipwrecks in our lagoon and it would be a devastation if they all start leaking."
