More than one hundred metres beneath the Mediterranean, HMS Olympus sits upright on the seabed outside Malta’s Grand Harbour covered in black corals. The submarine sank during the Second World War after striking a mine, taking 89 lives with it. Today, it remains a war grave but it has also become something else.

Its steel structure has become part of the underwater landscape. Gorgonians and other marine organisms grow across the wreck, while fish move around a vessel that was never meant to become habitat. For marine biologist Ella Zahra, HMS Olympus is one of the most fascinating wrecks in Maltese waters precisely because of this meeting of history and life.

A shipwreck may mark the end of one story. Underwater, however, another one begins.

Together with underwater archaeologist Maja Sausmekat, Ella works at Heritage Malta’s Underwater Cultural Heritage Unit, where archaeology, marine biology and conservation increasingly overlap. Their work asks a surprisingly complex question: What happens when a piece of human history becomes part of an ecosystem?

A Museum Beneath the Sea

Malta’s position in the centre of the Mediterranean has left an extraordinary archive beneath its waters. Ships, submarines and aircraft from different periods of history rest on the seafloor, each carrying its own story.

But unlike a temple, painting or historic building, this heritage is largely invisible.

Maja has noticed a striking difference between the way people relate to cultural heritage on land and underwater. A historic building can be visited and incorporated into everyday life. A wreck lying tens or even hundreds of metres beneath the surface is much harder to connect with.

That is where technology can help.

The team uses detailed imagery, 3D documentation and 360° videos to bring sites that most people will never physically visit back to the surface. During outreach events, visitors can virtually descend to the wrecks and explore them for themselves.

And people rarely see the same thing.

At one recent event, Ella remembers one child immediately focusing on species he recognised from fishing. Another was fascinated by the evidence of explosions and conflict. Show the same underwater scene to fifty people, Maja explains, and each may find a different point of connection.

For someone, a wreck is history. For someone else, it is marine life, a memorial or simply a glimpse into a world they have never seen before.

That personal connection matters. The aim, Maja says, is not to create an entire generation of underwater archaeologists. It is to plant a seed, an awareness and perhaps a love for the sea. Because once something is known and valued, there is a reason to protect it.

When a Wreck Becomes an Ecosystem

A ship sinking to the bottom of the sea introduces something very different from the sediment surrounding it: structure.

Over time, its surfaces can be colonised by marine organisms, turning wrecks into complex habitats. Fish find shelter around them, sessile organisms settle on their surfaces, and even the surrounding sediments can harbour distinct microbial communities.

For scientists, this makes wrecks much more than historical remains.

Heritage Malta’s WreckLife project brings archaeology and marine biology together to investigate these relationships. Existing records stretching back more than two decades can be combined with new surveys to explore how the organisms living on and around wrecks change through time.

A wreck is both the subject of history and part of the present-day sea.

Nothing Underwater Stays Still

There is one unavoidable problem: ships were not built to spend a century underwater.

Metal corrodes. Structures weaken. Sections collapse under their own weight. Currents, temperature, depth and exposure all influence how these changes unfold.

Rather than expecting a wreck to remain frozen in time, the team documents how it changes. High-resolution 3D surveys can create detailed records of a wreck at one point in time, allowing researchers to return later and compare structural changes.

For deep sites, this is particularly valuable because direct access can be difficult.

Maja’s favourite wreck, HMS Urge, is one of these sites. It was the first wreck she followed from its discovery through later stages of investigation, making its story personal as well as scientific.

The Pollution Hidden Inside History

But structural degradation presents another, more urgent problem.

Some twentieth-century wrecks sank while carrying fuel. Decades later, parts of that fuel may remain sealed inside degrading tanks and structures.

These are known as potentially polluting wrecks, or PPWs.

Researchers first need to understand which wrecks may still contain pollutants, how structurally stable they are and what could happen if that material escapes.

For Ella and Maja, this raises questions that are not only scientific but ethical.

Many wrecks are also war graves. They are the final resting places of people whose families may still commemorate them today. Disturbing such a site cannot be treated like an ordinary engineering problem.

At the same time, leaving a wreck untouched does not automatically mean preserving it. If its degradation threatens marine ecosystems or people living along the coast, intervention may eventually become necessary.

A wreck can remain historically significant even when action is needed to reduce its environmental risk.

Science Beyond the Scientific Bubble

The work behind all of this rarely fits into a predictable nine-to-five schedule.

A day at the Underwater Cultural Heritage Unit might begin with a dive, continue with hours of processing data and end at a public outreach event. During summer, fieldwork and diving become more frequent.

Ella estimates that an hour in the field can easily create many more hours of work afterwards. Still, this is her first major job after university, and what surprised her most was how little difficulty she has finding motivation for it.

Maja, after several years in the field, has come to value something similar: the importance of stepping outside disciplinary silos.

Science can become intensely specialised. But if knowledge never leaves that bubble — never reaches another discipline or the people whose heritage and environment are being studied — part of its value is lost.

Underwater cultural heritage makes that especially visible.

A wreck can bring together an archaeologist, a marine biologist, a technical diver, an engineer and a child wearing a VR headset. They may all look at exactly the same structure and see something different.

And perhaps that is precisely its power.

Shipwrecks are reminders of human history, but they are not disconnected from the living sea around them. They change, they become colonised, they create habitat and, sometimes, they carry environmental risks long after the events that brought them to the seafloor have faded from living memory.

Making these hidden places visible therefore does more than tell us about the past.

It gives people something beneath the surface to recognise, understand and care about.

And sometimes, protecting the sea begins exactly there with planting that first small seed of connection.

An article by Carina Zettel, based on an interview with marine biologist Ella Zahra and underwater archaeologist Maja Sausmekat from Heritage Malta’s Underwater Cultural Heritage Unit: underwatermalta.org Pictures by Ella Zahra and Maja Sausmekat