A liveaboard-only frontier of roughly 800 largely uninhabited islands in Myanmar's far-southern Andaman Sea, famous for the oceanic manta cleaning station at Black Rock and the nurse-shark tunnels of Shark Cave and Western Rocky. Trips run November–May from Thai ports with Burmese border formalities at Kawthaung — but Myanmar's post-2021-coup situation means checking current government travel advisories is part of planning.
Destination info
Conditions, highlights, and the resident marine life.
Conditions
Water and air temperature across the year.
WaterAirDryShoulderWet
Description
The Mergui (Myeik) Archipelago scatters some 800 mostly uninhabited islands across Myanmar's far-southern Andaman Sea. Closed to outsiders until 1997 and still tightly regulated, it remains one of Asia's least-dived frontiers: access is liveaboard-only, with boats departing the Thai ports of Ranong, Khao Lak or Phuket, clearing Burmese formalities at Kawthaung, then sailing to sites up to 100 miles offshore. The headline act is Black Rock, an 80 m-wide islet where nearly all of Myanmar's ~50 identified oceanic manta rays have been recorded at cleaning stations, peaking roughly January–April; Shark Cave (Three Islets) and Western Rocky add limestone tunnels patrolled by tawny nurse sharks, the Twin islands deliver clear-water pinnacle diving, and the remote Burma Banks — open-ocean seamounts rising from 250–300 m of water — are sometimes run as a separate silvertip-shark itinerary. Around 3,000 Moken 'sea gypsies', expert free-divers who have navigated these waters for centuries, inhabit the archipelago, some settled within Lampi Marine National Park, Myanmar's only marine national park. The season runs late October to early May (the southwest monsoon closes the area June–September), with 26–30°C water and visibility from 40 m at remote banks down to 5–20 m during the plankton blooms that draw the mantas and whale sharks. Be clear-eyed about context: since the February 2021 military coup Myanmar has been in armed conflict, Western governments advise against travel (UK FCDO: against all but essential travel to the far-southern archipelago area, as of January 2026; US: country-wide Level 4), and only a handful of Thailand-based liveaboards continued running Mergui itineraries through the 2025–26 season.
Highlights
What makes this dive worth the trip.
Black Rock is Myanmar's giant-manta headline: nearly all of the country's ~50 individually identified oceanic manta rays (Mobula birostris) in the Manta Matcher database were recorded at this single 80 m-wide islet. Marine Megafauna Foundation researchers led by Dr. Andrea Marshall documented a cleaning-station 'manta hospital' during the January–March peak and tracked the first recorded international manta migrations in Southeast Asia, between Myanmar and Thailand.
Access is liveaboard-only via Thailand: boats depart Ranong, Khao Lak or Phuket and complete Burmese border formalities at Kawthaung. The Myanmar entry permit (which includes a 30-day visa) takes at least 10–14 days to arrange, with government fees of roughly USD 170–250 plus THB 1,600 in park fees per diver — and only about three liveaboards listed Mergui itineraries for the 2025–26 season.
Plan with eyes open: as of 28 January 2026 the UK FCDO advises against all but essential travel to the far south of Tanintharyi Region — the area containing Kawthaung and the archipelago — and against all travel to most of the rest of the region, warning that the security situation may deteriorate at short notice and that travelling against its advice can invalidate travel insurance. The US State Department holds a country-wide Level 4 'Do Not Travel' advisory for Burma (updated May 2026).
Marine life
43 species you’re likely to encounter on a dive here.
Dive sites
6 signature sites at this destination.
Black Rock
An 80 m-wide islet standing alone roughly 100 miles northwest of Kawthaung — the most famous dive site in Myanmar and one of the most important oceanic manta aggregation and cleaning sites in the Andaman Sea, with mantas most frequent roughly January–April. Steep walls and banks drop away on all sides; sharks (silvertip, grey reef, whitetip, blacktip), marble rays, eagle rays and big schools of barracuda and batfish work the blue, with soft-coral growth on the deeper flanks. Currents can be strong with downward pulls off the rock tips, so it is treated as an advanced dive.
5–40 madvancedLiveaboardStrongVisibility 10–30 m
Shark Cave (Three Islets)
A limestone islet group in the central archipelago whose signature is a roughly 20 m tunnel cutting through the rock, its ceiling studded with cup corals and often packed with silversides and cave sweepers. Tawny nurse sharks shelter in the cave and under ledges — though sightings are less guaranteed than in the site's heyday — while the surrounding reef slopes to 25–30 m with ghost pipefish, seahorses, cuttlefish and hunting barracuda. Surge through the tunnel can be strong; torches are essential.
5–30 mintermediateLiveaboardModerateVisibility 10–25 m
Western Rocky
The southernmost flagship site, a small rocky island bored straight through by a tunnel that starts around 5 m and runs at up to 24 m through the island's heart — large tawny nurse sharks and giant lobsters are the classic residents. Outside the tunnel, walls and a cavern system drop to about 25 m and the surrounding reef reaches 40 m, with lionfish, moray eels, banded sea kraits, frogfish and ghost pipefish on the macro side and trevally and barracuda in the blue. Also one of the archipelago's best night dives.
5–40 mintermediateLiveaboardModerateVisibility 10–30 m
North Twin
One of a pair of offshore islands toward the western edge of the archipelago, dived mainly on its boulder slopes and the South Pinnacle from 3 m down to about 35 m. Clear oceanic water brings pelagic interest — manta rays and eagle rays pass through, zebra (leopard) sharks rest on the sand — while hawksbill turtles, cuttlefish, seahorses and ghost pipefish cover the reef and macro side. Currents can pick up around the pinnacle, but the site suits most experienced levels in fair conditions.
3–35 mintermediateLiveaboardModerateVisibility 15–30 m
South Twin
The gentler of the Twin islands: granite boulder gardens and coral slopes in usually calm, clear water, making it the archipelago's classic easy dive and a favourite check-dive or night-dive stop on Burma Banks itineraries. Whitetip reef sharks and tawny nurse sharks rest under the boulders, rainbow runners and barracuda school off the slope, and the rock faces hold ribbon eels, nudibranchs and other macro finds.
5–30 mbeginnerLiveaboardLightVisibility 15–30 m
Silvertip Bank (Burma Banks)
The best known of the Burma Banks — open-ocean seamounts far west of the archipelago whose flat hard-coral plateaus rise to about 15–24 m from surrounding water 250–300 m deep. This is remote, blue-water bank diving: silvertip sharks are the signature (they patrol the plateau edge and sometimes approach closely), with tawny nurse sharks, big potato grouper, dogtooth tuna, rainbow runners and barracuda. Strong, changeable currents make it advanced drift territory, and the banks are sometimes run as their own dedicated itinerary.
15–40 madvancedLiveaboardStrongVisibility 20–40 m
Where to dive & stay
Local dive centers, resorts, and hotels.
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