Potentially polluting wrecks: preserving the past without polluting the present
- info819852
- Sep 30
- 5 min read
Written by Iona Cargill, Marine Geophysicist and Archaeologist
It’s early July in Malta and I’m standing at the foot of the historic Fort St Elmo in the capital city of Valletta.
Whilst my feet gently burn on the baking tarmac, I prep my dive gear in the back of the truck. As a marine geophysicist and archaeologist, I grab any chance I can to explore the underwater world. On this occasion, I'm joined by two equally enthusiastic friends, a marine biologist and a marine ecology consultant. We’re all eager to get in the water, to escape the scorching heat of the Mediterranean sun, but mostly to be one step closer to our afternoon mission: exploring the wreck of HMS Maori.
The HMS Maori, a British tribal-class destroyer, sank in Malta Grand Harbour in 1942 after being hit by a German bomber. Proving to be an obstacle to traffic within the harbour, the wreck was scuttled in July 1945. The bow of the ship (forward section) was raised and sunk at St Elmo Bay where it continues to lay today. During the recovery operation, two twin guns were salvaged and repurposed, leaving behind the forward gun platforms. The partially submerged wreck contains the forward section of the engine and gear rooms, possibly still containing fuel tanks. It is a site of cultural interest, a habitat for marine life and, crucially, a ‘Potentially Polluting Wreck’ (PPW).
The name PPW refers to wrecks which hold vast amounts of oil, toxic chemicals and munitions which pose an increasing risk of leaking. Extreme weather events impact the structural integrity of the wrecks, whilst processes such as ocean warming and acidification contribute to the corrosion of the vessels. Exacerbated by climate change as well as the absence of appropriate management, the threat of these wrecks releasing their dangerous contents into the marine environment is increasingly present.
Navigating the rocky entrance and seaweed draped steps, we sink back into the lightly swishing waves. After a short traverse across the sandy bottom of St Elmo Bay, a vague silhouette starts to form amidst the sediment-rich, murky water. Protruding from the seafloor, tangled remnants of the vessel take shape.
As we edge closer to the crumbling bow of the ship, we stop to observe the number of marine species who have made The Maori its home. It’s striking to watch the abundance of life; miniature nudibranchs which cling to the decaying gun platform, rainbow fish swimming through the crevices and hermit crabs finding refuge in the dilapidated hull.
Significantly broken up and scattered, HMS Maori is showing signs of deterioration. The vessel lies near the corridor into Marsamxett Harbour, with a steady flow of marine traffic disrupting sediment and accelerating the rate of deterioration. Added to this, sitting in shallow water, the wreck is exposed to prevailing winds and storms making her vulnerable to further damage. As the wreck corrodes, we are losing a precious site of cultural heritage.
Additionally, as the HMS Maori decays, there is a heightened risk of contaminants leaking into the environment. This fragile situation is replicated globally, where the Maori – having had most munitions removed and repurposed - poses a relatively low risk compared to other PPWs with tonnes of toxic material still onboard.
Host to some of the world’s largest naval battles, the World Wars bore witness to the sinking of thousands of battleships, cargo ships, aeroplanes and U-boats. Plummeting to depths across our seas, these wrecks are most often sensitive war graves, the final resting place of many crew members. They now also serve as cultural heritage sites and homes to underwater ecosystems.
Like the HMS Maori, many of the wrecks also act as artificial reefs, serving as a place of refuge for diverse marine life. Having been submerged since the second world war or longer, many of these marine habitats and ecosystems are well established. If toxic materials are released into the environment, they can accumulate in organisms and infiltrate across ecosystem food webs.
As well as gradual leaks, there is a risk of large oil spills. As Charlotte Jarvis, Underwater Cultural Heritage Researcher, tells me: “If there is a catastrophic release of oil from one of these wrecks, entire coastal systems could be wrecked and livelihoods destroyed”.
Alongside posing risks to the environment and economy, PPWs are cultural heritage sites that could be lost. Marking the seafloor worldwide, they are symbols of the power and destruction of a global war and act as graves to those lives lost. As the structures disintegrate so does their legacy. These wrecks are significant historic resources that require monitoring and preservation for current and future research.
To find a solution to minimize the risks associated with PPWs, urgent and coordinated action is necessary. Attempts in this direction are being made, galvanising governments and concerned stakeholders.
Project Tangaroa are laying the groundwork for this. The organisation is focused on building a global framework, raising the profile of PPWs and facilitating cooperation. They report that an astounding 8,500 sunken vessels are classified as PPWs with an estimated 2.5-20 million tonnes of pollutants on board.
On June 11th, 2025, the International Council on Monuments and Sites (ICOMOS) and the International Union for Conservation of Nature (IUCN) released a joint statement on PPWs. They called on governments to take preventative action, to avoid the devastating consequences of substantial leaks or oil spills. Utilising innovative technologies to conduct non-intrusive surveillance of the wrecks was concluded to be the most cost-effective solution, avoiding heritage, human and environmental losses.
Following on from this, Tangaroa Project released a call to action under the title of The Malta Manifesto. The document calls amongst other things for empowering coastal communities and encouraging widespread data sharing to combat the risks posed by PPWs.
The work of Project Tangaroa has encouraged the development of citizen science programmes such as one led by Peta Knott from the Nautical Archaeology Society (NAS), equipping recreational divers and the wider marine community with skills and knowledge necessary to monitor these wrecks and feedback essential data.
Citizen scientists assess military wrecks to monitor for signs of structural collapse, clear cases of environmental pollution, damage from anchors or fishing gear and any evidence of salvage or collection of artefacts.
"This project lays the foundation for a truly impactful global monitoring network” explains Peta, “It’s the start of a movement that transforms casual observers into key players in protecting our oceans from polluting wrecks."
This system effectively reduces the risk of PPWs whilst safeguarding underwater cultural heritage.
As a recreational diver, I am very grateful to have access to incredible sites of cultural and environmental heritage such as the HMS Maori. But we must be mindful of the potential dangers of these wrecks, taking care not to disrupt them ourselves whilst actively monitoring for signs of collapse or pollution.
These increasingly fragile wrecks, facing inevitable deterioration, require quick action. By engaging governments, stakeholders and citizen scientists in a collaborative effort with a focus on prevention, it is possible to keep the ocean and our heritage safe.
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