In southern Italy's Tremiti Islands, diving helps protect the sea 

“See that cliff? That’s where we discovered black coral, 50 metres below the surface,” says diving instructor Adelmo Sorci, steering the inflatable boat through shimmering shoals of fish. In the soft morning light, the water around the Tremiti Islands is so transparent, I feel I could peer down and see the deep marine forest. But, for today at least, the sea keeps its secrets — much in keeping with the character of the region. “These are solitary islands,” says Adelmo, “a place that belongs to nature.”  

I’m on a tour with operator Marlin Tremiti around the five-strong archipelago off the coast of Puglia, Italy’s only island group in the southern Adriatic. Despite its diminutive size — barely more than a square mile of land in total — it’s been a marine reserve for almost 40 years. Sponges, molluscs, fish species like saddled seabream, damselfish, scorpionfish, dusky grouper — all can be spotted using only a mask and snorkel. Deeper down, black coral paints the seabed. 

“When I first came here 25 years ago on a diving trip, they were little more than a dot on the map, unknown even to Italians,” says Adelmo of the islands. Now, during the summer, the rich waters draw day-trippers from the Puglian coast and neighbouring Molise region, as well as some 2,500 longer-term travellers who spend the warm months here. “Then, by mid-September, everyone leaves and tranquillity returns.”  

With sun-bleached hair and tanned skin, Adelmo is one of roughly 400 year-round residents. He was born in central Italy’s Marche region, but his passion for diving brought him to San Domino, the Tremitis’ unofficial capital — where most ferries from the mainland dock — and one of two inhabited outposts in the archipelago. Here, he founded Marlin Tremiti, a dive centre that offers excursions and courses, as well as scenic boat tours.  

We circle San Domino. First comes Baia dei Pagliai, with towering limestone shaped like haystacks. Then, Cala degli Inglesi, where the steamship Lombardo — once commanded by Italian general Giuseppe Garibaldi during the military campaign that helped unify Italy — sank in 1864. Finally, Cala delle Rondinelle, named for the swallows (rondini in Italian) that nest here each spring.  

The sea mirrors the white cliffs, punctuated by dozens of caves. Above stretches a dense forest of Aleppo pines, their twisted trunks and canopy blanketing the island. A handful of whitewashed houses peek through, including the retreat once owned by the late Lucio Dalla, one of Italy’s most influential and beloved singer-songwriters of the last century, who found inspiration in the Tremitis’ quiet and its unspoiled nature. 

Adelmo brings my attention back to the beauty below. “It’s all an open-air laboratory,” he says, pointing to a buoy marking a spot where studies are taking place. Profits from Marlin Tremiti fund a scientific research arm, the Laboratory of the Sea. Like much of the Adriatic, the seabed of the Tremiti Marine Reserve is facing slow degradation. Meadows of Posidonia seagrass — which produce oxygen, absorb CO₂ and provide shelter for countless fish species — are threatened by heavy metals. Meanwhile, underwater archaeological sites found just a dozen metres from the shore — from 2,000-year-old shipwrecks to Second World War bombers — are increasingly vulnerable to corrosion. 

Every day, Adelmo and his team of geologists and marine biologists collect data and develop practical solutions. They raise awareness by organising seabed clean-ups and hosting summer events like the San Domino Posidonia Festival, which features talks with researchers, underwater photographers and other experts. Their latest initiative is Project 3DM/IT, modular structures produced using zero-impact materials. “Once placed on the seabed, they’ll encourage marine regeneration, acting like an artificial reef,” explains Adelmo. “I hope they can eventually be replicated around the world.”  

The same love of the sea that brought Adelmo here is what pulls Tremitesi back to their home islands year after year. “The lack of schools forced many families to move to the mainland,” says Enrico Massone, a young islander I meet later that day, pointing towards a group of children playing in San Domino’s central square. The piazza is small and paved white, with benches, palm trees and low buildings housing a few bars and restaurants. “Living here out of season isn’t easy.” 

During the winter, Enrico stays on the mainland with his wife Marta and their four-year-old son. But, like many Tremitesi, he returns as soon and as often as he can. In summer, he takes visitors on trips around the archipelago on his boat, the Sagittario. “This is where our roots are — and perhaps our future lies,” he says. “These islands, with their handful of beaches, and their evenings where going out for dinner is about as lively as it gets, have something truly magical.” 

Island ways 

The next morning just after sunrise, I set off from my accommodation, the local outpost of Touring Club Italiano (TCI), Italy’s main national tourist organisation, along San Domino’s coastal path. The trail is well maintained, and the walk begins spectacularly with a lookout over Cala Matano, a tiny cove cradled by Aleppo pines and limestone cliffs, where the sea shifts from turquoise to emerald to deep indigo. The island’s finest corners are earned rather than found, the descents over rocky ground as demanding as the climbs back up, but the reward comes in the form of deserted coves and views over sea caves I’d explored by boat the previous day.  

The colours of wildflowers and scent of mastic trees accompany me to the lighthouse at Punta del Diavolo, the westernmost tip of the island, the only place where San Domino is barren and windswept. Birds of prey, little terns and yellow-legged gulls all nest here — as well as the famous Diomedean bird, better known as Scopoli’s shearwater. 

“It sounds like a newborn baby crying out from the sea,” says Maia Quinti, the TCI’s resident marine biologist, as we head out that night. Once a week, she leads after-hours hikes to a lookout above Grotta del Bue Marino to listen for the haunting calls of these nocturnal seabirds, which rely on sound to navigate and communicate in the darkness.  

“Legend has it this is where they were born,” Maia explains of the protected animals, which return each breeding season to the towering cliffs on the northern coast of San Domino from the warm shores of Africa. “After the Greek hero Diomedes was killed in the archipelago, his companions were transformed into these birds, whose mournful cries still lament his death.” That’s why, in ancient times, the Tremiti Islands were known as the Diomedean Islands.  

Unfortunately, the moon is out tonight, and the birds quiet. Still, it’s moving to wait for them in the dark, in such a solitary part of the island. I think back to what Adelmo told me and realise he was right; whether it’s the black coral deep under water or the Diomedean birds flying just out of view, the most beautiful things here belong only to nature.