Seychelles Undersea: Dive into Paradise with Our Expert-Approved Guide to the Best Dive Sites

Seychelles has designated 210,000 square kilometres of its Indian Ocean waters as Marine Protected Areas — a zone roughly the size of Great Britain where dredging and oil prospecting are banned and tourism is tightly regulated. That legal protection, combined with an archipelago spanning 1,300 kilometres from granitic inner islands to coral outer atolls, creates a dive geography that splits into two fundamentally different experiences: the accessible, day-trip-friendly sites around Mahé and Praslin, and the expedition-grade outer islands where marine life density rivals anything in the Indian Ocean.

Shark Bank & North Sister Bank — Pelagic Action Close to Mahé

Shark Bank sits about 8 kilometres northwest of Mahé, a granite seamount that rises from 60 metres to 18 metres. It’s one of Seychelles’ Top 500 dive sites and the inner islands’ most reliable spot for pelagic encounters. Whale sharks appear here during the southeast monsoon between May and October, when nutrient upwellings draw plankton feeders. Grey reef sharks patrol the deeper ledges, and schools of trevally and barracuda work the water column above the boulders. The site demands moderate to strong current management — Advanced Open Water with drift experience is the realistic baseline.

North Sister Bank, another exposed granite pinnacle in the same offshore zone, attracts whale sharks most consistently during the northwest monsoon transition periods from March to May and again in November. Its vertical walls drop beyond 40 metres, creating upwelling conditions that concentrate fusiliers, snappers, and hunting grey reef sharks. Visibility here typically ranges 15–25 metres, though it can drop to 10–15 metres during plankton blooms — the same blooms that bring the whale sharks. Mahé-based day boats reach both sites in about 45 minutes, and most operators run early morning departures to beat the afternoon wind.

Wreck Diving — Ennerdale, Aldebaran & Twin Barges

Seychelles isn’t a wreck-diving destination on the scale of Truk Lagoon or the Red Sea, but it has three intentionally sunk or accidentally lost vessels that add variety to a week-long itinerary. The Ennerdale, a British Royal Navy Fleet motor tanker carrying 40,500 tons of oil, hit an uncharted rock off Mahé’s north coast in 1970 and sank in three sections at 30 metres. The stern section remains relatively intact — the wheelhouse and propeller are accessible, and soft coral colonisation has softened the steel structure enough that the wreck feels more like a reef than a shipwreck. The Aldebaran was confiscated for illegal fishing and scuttled in 2008 as an artificial reef during the Festival of the Sea. It lies between 30 and 40 metres and now hosts resident sharks and large schools of yellow snapper. Closer to shore, the Twin Barges sit in 18–22 metres off Mahé, their steel frames densely draped in soft coral. Current here is light to moderate, making it the most accessible wreck dive for divers working on buoyancy control.

Praslin & La Digue — Beginner-Friendly Reefs and Shark Schools

The inner island cluster of Praslin and La Digue offers a different pace from Mahé’s offshore pinnacles. Aquarium, off Praslin’s northeast coast, lives up to its name: 5–15 metres deep with negligible current most of the year, visibility regularly 15–20 metres, and fish density high enough that the dive feels rewarding even if your buoyancy is still a work in progress. Boat transfer from Praslin takes about 12 minutes. Anse Lazio Reef, also on Praslin, runs 6–14 metres with light current and good coral cover — a solid second dive for the same morning. On La Digue, Marianne Island delivers large numbers of grey reef sharks, along with turtles and moray eels, in 15–30 metres. Current here can pick up, so Intermediate-level comfort matters. Ile Cocos, also off La Digue, offers a shallow reef from 5–18 metres where light to moderate current can increase unexpectedly — confirm conditions with Trek Divers or Azzurra Pro Dive before entry.

Aldabra Atoll — The Expedition Dive

Aldabra Atoll sits 1,150 kilometres southwest of Mahé, a UNESCO World Heritage Site that holds the world’s largest population of giant tortoises and a fringing reef system effectively untouched by fishing pressure. Getting there requires a dedicated liveaboard expedition of 7–10 days departing from Port Victoria. The isolation is the point: the atoll’s reef supports grey reef sharks, hammerheads, and turtle populations at densities the inner islands cannot match. Visibility on calm inter-monsoon days regularly exceeds 30 metres. Aldabra ranks in the Top 500 dive sites twice — as both a destination and a specific site — reflecting its exceptional status.

Desroches, Alphonse & Astove — Outer Island Drift Diving

The outer islands of Desroches, Alphonse, and Astove sit on a coralline platform geologically distinct from the granitic inner islands. The topography shifts to atoll-style drop-offs, channels, and passes where pelagic encounters are not incidental — they’re the point. Desroches Channel runs 15–35 metres deep with current pushing 2–3 knots on spring tide. One logged dive there delivered a bumphead parrotfish school, two oceanic whitetip sharks, and a napoleon wrasse. Getting to Desroches can involve weather holds — one liveaboard trip recorded an 11-hour delay from Mahé, which is normal in Seychelles’ inter-island logistics chain. Alphonse Atoll is reached by a 45-minute light aircraft flight from Mahé that books out months in advance. Its outer reef wall and passes offer the highlight diving of the Alphonse group. Astove, further south, rewards those who make the journey with near-pristine reef systems where visibility regularly exceeds 30 metres and shark populations show no pressure from fishing. These sites are accessible only via liveaboard or resort-based operations — none are day-trip sites from Mahé.

Seasonality & Logistics — When to Go and What to Bring

Seychelles sits outside the main tropical cyclone belt, so there’s no dramatic seasonal closure like the Gulf of Thailand or the northern Andaman Sea. But the two monsoon seasons affect site accessibility and visibility enough to shape a dive-focused itinerary. The northwest monsoon from November through March brings calmer conditions on the western coasts of Mahé and Praslin, with inner-island visibility improving to 15–25 metres. The southeast monsoon from May through October creates choppier surface conditions on exposed coasts but drives nutrient upwellings that attract whale sharks to Shark Bank and North Sister Bank. The inter-monsoon windows — April to early May and October to mid-November — deliver the best all-round conditions: light winds, visibility peaking at 20–30 metres across most inner-island sites and 25–35 metres in the outer islands, and pelagic activity at its strongest.

For gear, a 5mm full wetsuit is the standard recommendation — the water feels warm on the first dive but catches up on the second and third. A dive computer with wireless air integration, like the Garmin Descent Mk3i, makes tracking nitrogen load across multiple dives straightforward. If you’re shooting underwater, the DJI Osmo Action 6 Bundle handles good light and accessible depths well. Marine park entry fees apply at some sites, and Seychelles enforces strict conservation laws with heavy fines for damaging coral or disturbing marine life — fines that apply to divers and snorkelers alike.

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Seychelles Diving — Before You Go

Do I need a visa to dive in Seychelles?

No visa is required in advance. All nationalities receive a free visitor’s permit on arrival valid for up to 30 days, extendable to 3 months. You need proof of accommodation, a return ticket, and sufficient funds — roughly $150 USD per day. Regulations can change, so confirm current entry requirements with the official travel portal before you book.

What certification do I need for the best dive sites?

For inner-island sites like Aquarium and L’Ilot, Open Water certification with fewer than 20 dives is fine. Shark Bank and North Sister Bank demand Advanced Open Water with drift experience. The outer islands — Aldabra, Desroches, Alphonse, Astove — require 50–100+ dives, drift experience, and comfort with strong currents at depth. Don’t treat certification alone as sufficient; current and remoteness add genuine risk.

Can I dive the outer islands without a liveaboard?

No. Aldabra, Desroches, Alphonse, and Astove are accessible only by liveaboard departing from Mahé or by light aircraft (Alphonse has a 45-minute flight that books out months in advance). None are day-trip sites. If a resort package on Mahé or Praslin doesn’t include a liveaboard leg, you’re limited to the 47 inner-island sites — which are good, but fundamentally different diving.

What’s the single biggest risk for divers in Seychelles?

Medical remoteness on outer-island dives. Aldabra and Astove are far from any hyperbaric chamber — the nearest decompression facility is on Mahé, and evacuation takes hours. A decompression incident at Astove becomes a serious evacuation problem. DAN insurance, a dive computer with conservatism settings, and disciplined surface intervals are non-negotiable for outer-island diving.

Closing

The coral superhighway that connects Seychelles’ reefs — larvae drifting between distant islands on Indian Ocean currents — is a reminder that this archipelago’s marine life operates at a scale most tropical destinations can’t match. Whether you log your first 12-metre dive at Aquarium or commit to a week-long Aldabra expedition, the same current system connects them. For a different perspective on what lives above the waterline, our guide to encountering giant tortoises and exotic birds in the Seychelles rounds out the trip.

References

Scuba Travel. “Seychelles Diving.” Scuba Travel UK, 2024. ↗

Underwater Atlas. “Seychelles — Dive Guide & Best Dive Sites.” Underwater Atlas, 2024. ↗

KOEK Diving. “Best Dive Sites Seychelles — A Field Ranking That Doesn’t Flatter.” KOEK, 2024. ↗

Underwater Atlas. “Seychelles Destination Overview.” Underwater Atlas, 2024. ↗

If you’re building a longer Seychelles itinerary, our guide to Vallee de Mai and other UNESCO World Heritage sites on Praslin pairs well with a diving trip, and our whale shark diving guide goes deeper into timing those encounters. For dry-land adventures, hiking Morne Seychellois National Park offers views across the same granite islands you’ve been exploring underwater.