Seychelles’ Outer Islands: Journey to Remarkable Remote Paradises

The Seychelles archipelago spans 115 islands across the Indian Ocean, yet only 2 percent of its roughly 120,000 residents live on the 72 coral atolls and sand cays that make up the Outer Islands — known locally as Zil Elwannyen Sesel. Tourism minister Amanda Bernstein describes the country as offering a “genuinely untouched feel,” and it’s this quality that draws around 350,000 visitors each year, most of whom never leave the granite Inner Islands of Mahé, Praslin, and La Digue. The Outer Islands are a different proposition entirely: fly two hours south of Victoria and you’re in a landscape where seabird colonies fill the sky, reefs drop nearly a kilometre into darkness, and conservation isn’t an afterthought but the operating model. This guide covers the five atolls that define the experience — Alphonse, Astove, Cosmoledo, St François, and Aldabra — and what it actually takes to visit them.

Alphonse Island — the gateway to the Outer Islands

What does a genuinely low-impact eco-resort look like when there’s no nearby town to supply it? Alphonse Island, 400 km southwest of Mahé, offers a working answer. The 29-key Alphonse Island Lodge runs mostly on solar power, treats its own wastewater, collects rainwater, and operates a 4-hectare bio-intensive farm that produces up to 4.5 tonnes of crops each month — supplying roughly 90 percent of the plant-based food across all Blue Safari properties in the Outer Islands. Overwater bungalows are prohibited; the model here is barefoot eco-lodge, not Maldivian-style luxury.

Blue Safari, founded in 2012 by South African-born Seychellois Murray Collins and fly-fisher Keith Rose-Innes, took over the lodge after earlier tourism efforts collapsed during a decade of Somalian piracy. “You used to have to go fishing with an armed escort,” Collins has said. Today the operation runs the Alphonse Foundation, an NGO that works with the Ministry of Agriculture, Climate Change and Environment and the Island Conservation Society to survey fish populations, coral health, and migratory birds. In 2023 the foundation tagged 32 sharks across five species (lemon, grey, reef, silvertip, bull) and 20 manta rays the year before. Diving instructor Andrew Irwin puts it bluntly: “In Indonesia you’re guaranteed not to see a big shark. Here you might see one at any moment.”

Astove Atoll — where the reef drops into darkness

Getting to Astove isn’t cheap or easy, and that’s precisely the point. At roughly 1,000 km from Victoria — two plane rides and closer to Madagascar than to Mahé — Astove is one of the most southerly of the 72 uninhabited atolls in the Outer Islands. It encircles a 21 km² lagoon with a strip of land so narrow that migratory birds use it as a landing strip and green turtles nest on sand flats “powdery as virgin snow,” as one account describes it. A ghost yacht named Shangri-La lies beached on the northwesterly shore; its origins are unknown, but it’s a fitting emblem for a place where reefs have destroyed vessels since the 16th century.

The reef wall that rings Astove drops 900 metres — nearly 3,000 feet — into what was once called the Sea of Zanj. Jacques Cousteau filmed parts of his 1956 documentary The Silent World here, pioneering underwater colour photography in waters that remain among the least-explored dive sites on the planet. Snorkellers float above a vertical coral garden where bluestripe snapper and Napoleon wrasse move in synchronized battalions among roughly 1,000 recorded fish species. The drop-off creates the sensation of floating over open space: half a mile of blackness beneath you, light bars filtering through swarms of juvenile fish above the reef. Accommodation is the six-room Astove Coral House, starting from around US$1,100 per person for a three-night package that includes hiking the lagoon, exploring the mangroves, and walking the reef flats at low tide.

Cosmoledo Atoll — seabirds, groupers, and a camp designed to vanish

If Alphonse is the comfortable gateway and Astove is the deep-wall dive, Cosmoledo is the raw wildlife experience. A two-hour flight southwest from Alphonse delivers you to a 5 km² crescent of sand that rings a lagoon 28 times its size. Blue Safari’s Cosmoledo Eco Camp consists of eight converted shipping-container rooms designed to be disassembled with almost no trace — the camp crouches low among beach cabbage bushes, and the whole operation runs November through April, then packs up.

The wildlife density here is staggering. Cosmoledo is an Important Bird and Biodiversity Area with the largest breeding colonies in Seychelles of three booby species: red-footed (the largest population in the western Indian Ocean), masked, and brown. Red-footed boobies sit in trees like thousands of magnolia blooms, cocking their heads in unison and emitting a guiro-like rattle; when flustered they produce a sound like herds of animals hiding in a single tree. Masked boobies come in to land at the speed of frisbees. On South West Island and Grand Polyte — two of Cosmoledo’s 20-plus named islets — a rat-eradication programme has caused an explosion in seabird numbers. Elle Brighton, Blue Safari’s ecology and sustainability manager, explains the logic: “Oceanic seabird colonies are diminishing in the Indian Ocean. If you put a big hotel on an atoll, the birds disappear.”

In the water, the spectacle is equal. Lemon shark pups with gooseberry-coloured eyes cruise the shallows; juvenile blacktail snappers and giant batfish form dense schools. The velvety coral zones host groupers at a scale most divers never encounter: goliaths over a metre long, potato groupers with giraffe-like patterns, saddlebacks neon as glow sticks, and gaudy African marbled specimens. Coconut crabs — the world’s largest terrestrial arthropod — have a habit of stealing sandals left outside the eco-pods. Guides on the atoll also help police against piracy and poaching; soon a permanent conservation team will be based here.

St François Atoll — a potential manta ray nursery

Twenty minutes south of Alphonse by boat, St François is a 2 km-long atoll with a lagoon three times the size of Alphonse’s. In 2023 it was designated an Important Shark and Ray Area, and researchers believe it may be one of only five confirmed manta ray nurseries globally — a status that would make it globally significant for a species already in drastic decline, partly due to demand for ray gills in traditional Chinese medicine. On the boat ride over, 50-plus spinner dolphins often accompany the crossing, moving in coordinated arcs alongside the hull.

The manta encounter itself is the kind of experience that rewires your expectations of what’s possible in the Indian Ocean. A female manta with a 3.9-metre (13-foot) wingspan glides like a winged ribcage through the current streams, turning to examine divers with what one observer described as “intelligent eyes.” When a squadron of rays appears, they circle and dive like giant kites caught in a sudden cyclone. The search involves scanning the lagoon mouth for shadows on the edge of current streams — still patches smooth as polished black marble — then kitting up and slipping into the water when movement is spotted. There’s no guarantee of an encounter, but the probability here is higher than almost anywhere else in the region.

Aldabra Atoll — the expedition finale

Aldabra Atoll, a UNESCO World Heritage Site, is the crown jewel of the Outer Islands — and the hardest to reach. It hosts over 150,000 Aldabra giant tortoises, the largest population of the species anywhere, and one of the largest green turtle breeding populations in the western Indian Ocean since Seychelles banned turtle hunting in 1994. The atoll’s isolation has protected extraordinary biodiversity: giant tortoises move through natural habitat rather than a sanctuary enclosure, seabird colonies fill the sky, and the lagoons and mangroves support a density of life that makes the journey feel like a natural-history documentary rather than a holiday.

The most practical way to visit is via Aldabra Expeditions, which operates 9-night nature voyages aboard the 30-metre expedition yacht MY Basilisk. The published 2026 departures run October 10–19 and October 19–28, with a route that links D’Arros, St Joseph, Alphonse, Bijoutier, Cosmoledo, Assumption, Astove, and Aldabra itself. Starting pricing is around €4,800 for the 10-day programme, though cabin availability, flights to and from Astove, and exact inclusions should be confirmed directly before booking. This is not a cruise in the conventional sense — there are no port days, no fixed schedules, and access to each atoll depends on weather, tides, and conservation rules. The operator recommends arriving on Mahé at least one night early and building in a buffer night at the end before any international connection.

Getting there, when to go, and what to bring

Access to the Outer Islands funnels through Mahé. The first step is a 16-seater Beechcraft jet from Seychelles International Airport to Alphonse (about 400 km, roughly an hour). From Alphonse, smaller planes and boats connect to Astove, Cosmoledo, and Aldabra — each leg adds travel time and cost, and schedules are driven by weather and conservation logistics rather than airline convenience.

Seasonal windows are narrow and vary by atoll. Alphonse operates year-round as the hub. Cosmoledo Eco Camp runs November through April; Astove Coral House runs November through March. Aldabra Expeditions’ 2026 voyages are limited to two 10-day windows in October. The southeast trade winds blow from July through August, bringing dry weather and bright skies to the Inner Islands but rougher conditions in the outer atolls. For the southern atolls, the calmer months generally fall between November and April.

Packing is straightforward if you accept that comfort comes from preparation, not from infrastructure. Reef-safe sun protection, quick-dry clothing, water shoes (essential for champignon coral), a rash guard, and your own mask if fit matters are the basics. The Aldabra Expeditions operator adds that you should arrive physically comfortable getting in and out of small boats in moving water — there are no jetty landings at most sites.

Seychelles’ Outer Islands — what to know before you go

Are the Outer Islands safe for independent travellers?

Yes, but you’re not truly independent once you leave Mahé. The Islands Development Company (IDC) manages all Outer Islands development and strictly controls access. You book through one of two operators: Blue Safari for Alphonse, Astove, and Cosmoledo; Aldabra Expeditions for Aldabra. There’s no ferry service, no public accommodation, and no way to island-hop without a pre-arranged itinerary.

How much does a trip actually cost?

Alphonse Island Lodge starts at US$4,584 per person for three nights. Astove Coral House runs from around US$1,100 per person for three nights. Cosmoledo Eco Camp starts at US$1,404 per person and operates only November–April. The Aldabra expedition starts at roughly €4,800 for the 10-day programme. None of these figures include international flights to Mahé or the connecting flights to the atolls — factor in an additional US$500–1,000 for the domestic air transfers.

What’s the biggest practical challenge?

The distance and the weather dependency. Astove is 1,000 km from Mahé — two plane rides and a boat transfer. Aldabra adds another leg. The 2024 bleaching event affected Seychelles reefs, and if current warming trends continue, the region could lose 90 percent of its coral by 2050. Check current conditions with your operator before booking, and build in at least one buffer night on Mahé at both ends of the trip.

Can I visit if I don’t dive?

Yes. Snorkelling at Astove’s reef wall, floating above the 900-metre drop-off, and watching the manta rays at St François are all surface-level experiences. The seabird colonies on Cosmoledo and the giant tortoises on Aldabra are terrestrial. That said, the Outer Islands are fundamentally marine environments — the best moments happen in or on the water, and comfort with small boats and moving water is essential.

Is this suitable for families with children?

It depends on the children. The long travel legs, the lack of conventional entertainment, and the physical demands of getting in and out of boats make it a poor fit for younger kids or anyone who needs a predictable daily schedule. Teenagers with a genuine interest in marine biology, birding, or photography would find it extraordinary. Blue Safari’s lodges and the Aldabra yacht can accommodate families, but the experience is expedition-grade, not resort-grade.

Closing

The Outer Islands don’t offer a polished version of Seychelles — they offer the version that existed before tourism arrived. Ninety-nine percent of the country’s territory is ocean, and the atolls scattered across it hold some of the healthiest reefs, densest seabird colonies, and most untouched marine environments in the Indian Ocean. The journey to reach them requires time, money, and a willingness to let weather and tides set the agenda. But for anyone who makes it, the reward is a place where the wildlife still outnumbers the visitors, and where the line between traveller and naturalist dissolves in the water. For more on how the Inner Islands balance tourism with conservation, see our guide to sustainable travel practices across the Seychelles.

References

Seychelles Tourism Board. “Outer Islands.” Seychelles.com. ↗

Blue Safari Seychelles. “Alphonse Island Lodge, Cosmoledo Eco Camp, Astove Coral House.” BlueSafari.com. ↗

Aldabra Expeditions. “Nature Voyages Aboard MY Basilisk.” AldabraExpeditions.com. ↗

Four Seasons Resort Seychelles. “Petite Anse, Mahé.” FourSeasons.com. ↗

If you’re still planning your route through the main islands, our guides to Mahé’s best beaches and Creole culture and Praslin’s Vallée de Mai and hidden gems cover the Inner Islands in detail. For divers, Seychelles’ undersea wonders maps the best dive sites across the archipelago. And if you’re curious about the country’s conservation milestones, Seychelles wildlife encounters covers the giant tortoises and rare bird sanctuaries that make these islands so remarkable.