How a Country Turned Shipwrecks into Underwater Cities

On the sonar display inside the cramped cabin, outlines emerge where the chart says there should be nothing but sand. Beyond the window, the sea is empty, level and unconcerned. Yet 20 metres down, a whole city is beginning to stir.

A dive team tips backwards into the water as bubbles crackle upwards. Their torches cut through the blue until they reveal something that has no business being there: the corroded bow of a 90-metre vessel, lying undisturbed on the seabed. Nearby, concrete blocks stand like unfinished tower blocks, their surfaces already coated with pink and orange life.

Fish gather in dense, shimmering shoals. Coral gradually spreads across scars in the metal. Turtles drift cautiously between the structures, like new residents unsure of their surroundings. A decade ago, none of this was here.
Every structure is artificial.
The life is not.

How a country transformed shipwrecks into underwater cities

At an ageing naval dock shortly before sunrise, a decommissioned warship awaits its final assignment. Welders make the last adjustments to its openings, engineers inspect the ballast for a third time, and a small group of local residents stands by the railings with coffee in hand. Diesel fumes mingle with the smell of salt water.

The vessel once guarded national borders. Now it is being readied to become the base of a future reef. Openings have been cut into the hull so that water and fish can move through it, fuel tanks have been thoroughly cleaned, and hazardous materials have been removed. The huge steel ship appears damaged, almost bare-boned, but it retains an unexpected dignity. Within hours, it will slip beneath the surface and begin a second existence no one present could have envisaged when it was first launched.

This is no isolated publicity exercise. It has become a national policy. During the past several years, the country has discreetly sunk dozens of retired ships and placed thousands of specially built concrete modules along its coastline. The ambition is both bold and remarkably straightforward: to rebuild damaged marine habitats from the ground up, using man-made structures as a framework that allows wild life to return.

One of the first locations lies offshore from a quiet fishing town where annual catches had been falling for years. Local people still recount the first dive to the newly submerged freighter. Initially, there was only stillness, sand and the unsettling mass of the ship lying on the seabed like a ghost.

When divers returned three months later, algae and sponges had lightly covered the hull, resembling the first marks on an untouched wall. Small damselfish flashed in and out of the portholes. One grouper had already taken possession of the shade beneath the bow. A year later, nearby lobster traps began to come up heavier. They were not full, and not comparable to the catches of earlier times, but they were no longer painfully empty.

Today, that wreck draws visitors. Snorkelling operators schedule departures around the tides, while the harbour car park fills with vans carrying tanks and fins. A recent survey identified more than 120 species around the artificial reef, including species that had disappeared locally years earlier. Fishers still complain, as fishers tend to do, but many now acknowledge that the offshore structures have become nurseries that send life back towards the shore.

The reasoning behind these underwater projects is strikingly simple. Marine ecosystems require three essentials: solid surfaces that organisms can colonise, protection from predators and currents, and sufficient undisturbed time for food webs to recover. Sandy seabeds, which extend across vast areas of coastal waters, provide little of this by themselves.

Ships and concrete modules alter those conditions. They create cliff-like structures where only flat plains once existed. Their hollows and ledges form microhabitats, from shadowy gaps for crustaceans to smooth surfaces where corals, oysters and algae can attach. Once that first layer of life takes hold, the rest follows: plankton feeders first, then smaller fish, then predators. In a few years, what began as rusted steel and grey cement can resemble and function like a natural reef, even when its underlying form originated on an engineer’s computer.

There are risks, naturally. Put unsuitable structures in the wrong location and the result may simply move the damage elsewhere or introduce fresh pollution. This is why the country shifted away from disorganised local “reef projects” towards a coordinated scheme involving marine biologists, coastal engineers and fishing communities. Artificial reefs are not a miracle solution. They are tools, and like any tools, they can cause harm or deliver benefits according to how they are used.

The careful work of creating artificial reefs from scrap

Every dramatic video of a ship being sunk is preceded by months of painstaking, unglamorous preparation. The team returns to one requirement repeatedly, almost as a mantra: the structure has to be clean. Fuel tanks must be emptied, loose cables removed and toxic paint prevented from flaking away. Any compartment that could trap air is opened, ensuring that the vessel settles safely rather than becoming an underwater time bomb.

A second principle concerns form. Marine architects now create some artificial reef modules from the outset, using 3D models to anticipate the way currents will flow around them. They include fish tunnels, build flat areas for coral fragments and make rounded openings that allow light to enter the darkness. It is rather like planning a neighbourhood without knowing who will live there. Even so, years of experimentation have demonstrated that diverse, intricate forms support more abundant life than plain cubes or flat slabs.

The teams gained this knowledge through difficult experience. In the early years, well-intentioned local schemes threw everything from scrapped cars to old tyres into the sea, in the hope that life would somehow follow. On maps, those locations were labelled as “reefs”. Underwater, divers later discovered bleak, deteriorating rubbish dumps that snagged nets and released chemicals. Let us be honest: no one really does this every day, but decisions made in a single morning can haunt an ecosystem for decades.

The national programme now relies on tightly regulated materials: treated steel, marine-grade concrete and, in some cases, engineered ceramics designed to resemble natural rock. The approach has moved from disposal to deliberate design.

There is also a human dimension to this process of learning. One windy afternoon, a marine biologist I met stood against the rail of a research boat, observing a barge position a group of new concrete modules. She sounded both proud and wary.

“People think we’re ‘creating’ nature,” she said. “We’re not. We’re creating opportunities. Life does the rest, if we stop getting in its way.”

That distinction guides everyday decisions within the programme. Rather than installing artificial reefs everywhere, teams chart migration routes, spawning sites and fishing activity before preserving buffer areas where the sea can follow its own patterns. They consult fishers before lines are drawn on maps, seeking to prevent collaboration from turning into conflict.

• Select places where natural reefs once prospered, rather than arbitrary bare seabeds.
• Choose clean, long-lasting materials that will neither leach toxins nor deteriorate rapidly.
• Pair artificial reefs with fishing restrictions instead of using them to avoid those restrictions.
• Observe sites for years rather than months to measure genuine ecological change.
• Bring local communities into the process early, so that “their sea” does not feel as though it has been taken from them.

At a deeper emotional level, this work demands a kind of double vision. It requires looking at a lifeless coastline while imagining colour returning gradually. It also means accepting that certain losses will not be reversed within a human lifetime. Scientists here speak quietly of “triage” - deciding where resources should be concentrated and where the only option is to safeguard what remains. It is not a heroic narrative. It is an honest one.

What artificial reefs reveal about our relationship with the sea

Diving at one of these artificial reefs changes how the news is received. Reports of coral bleaching, declining fish stocks and warming seas can feel overwhelmingly vast. Then there is the memory of hovering beside a porthole, watching an entire fish community defend its tiny section of hull as though it were the centre of the universe.

During a night dive, the same wreck becomes something entirely different. Octopus arms probe the edges of concrete arches. Shrimp eyes catch the beam of a torch like tiny red LEDs. Thick layers of life soften the vessel’s artificial contours, as though nature were gradually wiping away its human backstory and replacing it with another of its own. The effect is both unsettling and oddly reassuring. We made this, certainly, but we are plainly not in control beneath the surface.

That reversal contains a quiet lesson. For decades, people have chiefly altered the ocean through extraction: catching fish, dredging sand and drilling for oil. Here, by contrast, the alteration involves adding structure and then withdrawing. There is something almost modest about it. We’ll give you walls, says the programme to the sea. The rest is up to you.

This does not make artificial reefs a silver bullet. They may draw fish away from natural reefs and create a misleading appearance of abundance. If regulations are ignored, they can turn into centres of overfishing. They can also fail, becoming lifeless monuments in seas made warmer and more acidic. On a bad day, the idea can resemble rearranging furniture in a house that is slowly flooding.

On a good day, however, these reefs suggest something very different: a rehearsal. They show that, with some assistance and less pressure, marine life remains remarkably able to recover. The question that lingers after every dive, meeting and ship sent to the seabed is both simple and weighty.
What might happen if this mindset were scaled up, rather than only the structures?

Most of us have experienced the moment when a childhood landscape suddenly seems smaller, barer and emptier than memory suggested. For many coastal communities, the sea has undergone the same contraction. Grandparents’ stories of packed shoals and noisy reefs can now sound almost legendary. Watching a dead expanse of sand become a living, shifting maze over several years does not remove that grief, but it offers something gentler: it makes “too late” seem less final.

Perhaps that is the understated strength of artificial reefs. They make no claim that the damage never occurred. Nor do they recreate a fixed image of some earlier time. Instead, they provide a rough bridge of steel and concrete between what has been broken and what might still develop. Imperfect. Industrial. Real.

And after seeing an entirely new ecosystem form around the skeleton of a discarded ship, it becomes more difficult to believe that humans can play only the villain in the story of the sea. Another script is available - neither heroic nor pristine, but possible. One ship, one block and one new reef at a time.