Picture this.

“You’ve got a really healthy ecosystem with amazing corals and healthy marine life on these amazing structures,” says Matt Carter, Research Director at ocean research and conservation charity Major Projects Foundation (MPF). “And then inside these ships there’s thousands and thousands of liters of oil that’s potentially going to wipe out all this marine life.” While it might sound like a movie script, this isn’t a hypothetical scenario.

Exploring shipwrecks is a popular form of recreational scuba diving, and wrecks make up some of the world’s most famous dive sites. Some of the most famous include: the SS Yongala in Townsville, Australia—a luxury passenger ship that sank in a storm in 1911; Egypt’s SS Thistlegorm, a British army freighter sunk by bombs on just its fourth voyage in 1941; the German Fleet in Scapa Flow, Scotland, which was scuttled at the end of World War I on the orders of a commander who didn’t want the ships to become spoils of war; and, of course, the spectacular shipwrecks found at the renowned Chuuk (Truk) Lagoon in the Pacific.

NEWSLETTERS Beast Travel Digest Get the entire world in your inbox. Subscribe By Clicking "Subscribe" you agree to have read the Terms of Use and Privacy Policy

“Why bother visiting a rusty old hunk of scrap metal?” non-divers might ask; especially those who aren’t particularly interested in how the wreck came to be at the bottom of the ocean. Those who imagine a wreck as a barren shell might be surprised to find these structures teeming with life, since shipwrecks act as an artificial reef that provides a habitat for coral and other sea creatures. Most of the passionate divers who come to explore these underwater playgrounds—packed with colorful corals, sponges, tropical fish and even sharks and rays—have little idea of the threat looming behind this beautiful ecosystem.

During World War II, over 3,000 ships—about 300 of them oil tankers—sank in the Pacific. As they rust, many are at risk of leaking oil, which could devastate the underwater ecosystem. Fish exposed to oil can have lower chances of survival due to stunted growth, altered heart and respiration rates, enlarged livers and impaired reproduction.

Determining which shipwrecks pose the greatest risk to the oceans—and getting to them before they leak—is a daunting task. The majority of the Earth’s oceans are unexplored and we have better maps of the moon than of the bottom of the ocean—so how is it even possible to know which of these ticking time-bombs might pose the biggest threat?

Marine archaeologist Matt Carter, Research Director at ocean research and conservation charity Major Projects Foundation (MPF)—along with partners from The University of Newcastle, Australia, and the Secretariat of the Pacific Regional Environment Programme (SPREP)—is working against the clock to find out. He’s just returned from a reconnaissance expedition to Chuuk (also known as Truk) Lagoon to establish the condition of some of the many wrecks in this diving hotspot.

“There’s about 65 shipwrecks on the lagoon and 17 are on our list of highest risk potentially polluting wrecks,” Carter told me. During this trip, he used 3D photogrammetry to create a model of the 9,627-ton Rio de Janeiro Maru. This enormous eight-deck passenger liner, which could carry over 1,100 passengers and 150 crew, has been lying on her starboard side at a maximum depth of just over 30m, slowly deteriorating since she was sunk in February 1944 by American aircraft.

Creating an accurate 3D model—made up of 7,331 photos of the Rio de Janeiro recording every single aspect of the wreck from multiple angles—was, in Carter’s own words, “a bit of a mission.” Capturing the photos of the 140m wreck involved over 3.5 hours underwater (broken up into three separate dives) taking photos every second. To make sure nothing is missed, each photo must overlap with the next by about 60 percent. “So, you can imagine swimming along and click, click, click,” he described. “When it comes together, it gives you a really detailed map of the wreck.”

While waiting patiently for the final image to be ready—so large it took days to process—he explained: “At the end of it we’ll have a 3D map with the most detailed resolution of the wreck that there’s ever been.”

Computer software called Agisoft Metashape turns these thousands of photos into a scalable 3D model to help Matt and his team get as much information as they can about the wreck; creating a visual inspection of its size and measurements, exactly what condition it’s in and where the fuel tanks are. You can even zoom into and rotate the model to get an accurate picture of its condition. The tool, he explains, “allows us to survey these wrecks faster and record them more accurately than ever before!” They will then compile an environmental risk assessment which considers how much oil might still be on the ship and, if nothing is done, what the environmental impact could be if—and when—it escapes. The information he gathers from this modeling is critical in determining what should be done next.

There’s no doubt the wrecks at Chuuk are deteriorating. Regular divers to spoke of seeing visible evidence of the wrecks collapsing over the years. Marine corrosion expert Dr Ian MacLeod, who is also part of the MPF, had previously estimated the wrecks in Chuuk Lagoon would enter a “peak leak” period, when they start to break down, around 2015 to 2020. “They’re really getting to the end of their life and collapsing significantly,” said Carter. Time is not on our side.

Nor is the climate. While healthy oceans produce over half of the world's oxygen, absorb carbon dioxide, and store excess heat in the atmosphere—all of which help us avoid the worst consequences of climate change—climate change itself is speeding up the degradation of these long-submerged wrecks. More severe storms increase the rate of corrosion and thus increase the chance of a leak.

It might be a silent threat, but the risk is significant. In 2001, a State of Emergency was declared in Yap State, Micronesia, when a sunken World War II US military oil tanker, the USS Mississinewa, started leaking oil in a remote atoll. A complete ban on fishing was imposed and the US Navy was brought in to conduct a major salvage operation, removing around 6,000 tons of oil from the sunken vessel. Many Pacific Island communities are worried about a similar situation happening if other wrecks in their waters begin to leak.

The 500-foot Shinkoku Maru oil tanker, one of the most popular dive sites in Chuuk Lagoon and another of MPF’s high priority wrecks, was damaged by Typhoon Maysak in 2015, although it’s still thought to hold a significant amount of oil. Diving this wreck on his recent Chuuk expedition, and seeing how much of an impact nature can have on big shipwrecks like this, was “a real eye-opener” for Carter. It’s also why these recon missions are so important. “We’d love to find out that there’s hardly any oil on them left but there’s no indications that that’s the case,” said Carter. With tankers still containing oil, another storm of that magnitude could be catastrophic. The worst-case scenario? A simultaneous release of oil from multiple shipwrecks.

It’s quite common to remove the oil from this kind of dangerous shipwrecks. The U.S. Coastguard removed more than 450,000 gallons of oil from the Coimbra shipwreck in July 2019. The previous October, the U.S. Navy recovered just under 230,000 gallons of oil from Prinz Eugen, a capsized World War II German cruiser. While a preventative clean-up operation can be expensive, cleaning up oil from a wreck that has already leaked is significantly more so.

So, while Matt and his team are finding the information critical to mitigating the risks of a potentially devastating oil spill, what else can be done to protect the wrecks at Chuuk and around the world?

These amazing archaeological sites are incredibly popular with divers—making tourism an enormous economic asset for the region—so responsible diver behavior is important in minimizing deterioration. Carter explains: “Good diving practices will help the wrecks maintain their strength as long as possible—not crashing into them and kicking them will help preserve them.”

Funding is also an issue. While in many places this type of work is being done by the likes of NOAA (in the U.S.) and the Ministry of Defense (in the U.K.), for countries such as Micronesia, Papua New Guinea and the Solomons, there’s very little money available for this type of operation. Of the 1,200 potentially polluting shipwrecks around the Pacific, Carter and his team at MPF have shortlisted the 50 highest risk wrecks and are calling for support to help protect them.

While there “hasn’t been much done” over the past 15 years of continued corrosion, Carter is hopeful of the increased concern for the ocean in recent years. Public support and donations could be a major factor in whether his team can protect the oceans from these wrecks. Whatever happens, it may well be “right at the last minute” because these wrecks, which are already collapsing substantially, “are going to rupture soon.”