Mergui Archipelago
The Mergui (Myeik) Archipelago scatters some 800 islands down Myanmar's Andaman coast, most of them unpeopled and rarely dived. Liveaboards working out of Kawthaung, opposite Thailand's Ranong, reach limestone pinnacles, tunnels, and the manta magnet of Black Rock in near-solitude. Access has always been paperwork-heavy, and since Myanmar's 2021 military takeover it has been intermittent; anyone considering a trip must check advisories and operator status first.
Why dive here
Mergui offers what the crowded Andaman largely lost: empty sites, big topography, and the feeling of exploratory diving on a comfortable boat. Black Rock is the anchor, a lone outcrop in open sea where oceanic mantas arrive through the season's heart and marbled rays pile on the ledges. Western Rocky threads a genuine tunnel clean through an island, its recesses sheltering tawny nurse sharks and lobsters, while the Twins serve current-washed boulder gardens and passing trevally. Macro life is dense and undervisited: tigertail seahorses, harlequin shrimp, frogfish, and nudibranchs on nearly every wall. Be clear-eyed about the rest. Shark populations were heavily fished long before tourism arrived, visibility swings with green thermocline layers, and itineraries bend to permits, weather, and politics. Most Western governments have advised against travel to Myanmar since 2021, and seasons have run irregularly; when boats do sail, they sail into some of Southeast Asia's least-dived water.
Month by month
The operating season, when trips run at all, spans roughly late October to early May, with the steadiest weather and the Black Rock manta window from about December to April; the southwest monsoon shuts the archipelago the rest of the year.
| Month | Water | Visibility | What it's like |
|---|---|---|---|
| January●●●●● | 26–28 °C / 79–82 °F | 10–30 m | Heart of the season; mantas working Black Rock. |
| February●●●●● | 26–29 °C / 79–84 °F | 10–30 m | Best odds of calm seas and big-animal action. |
| March●●●●● | 27–29 °C / 81–84 °F | 10–30 m | Season peak continues; plankton pulses vary visibility. |
| April●●●●○ | 28–30 °C / 82–86 °F | 10–25 m | Warming water; last full month of trips. |
| May●●○○○ | 28–30 °C / 82–86 °F | 8–20 m | Final departures early in the month as the monsoon builds. |
| June●○○○○ | — | — | Southwest monsoon; no trips. |
| July●○○○○ | — | — | Closed season across the archipelago. |
| August●○○○○ | — | — | Monsoon weather continues; boats stay in Thailand. |
| September●○○○○ | — | — | No access; seas remain rough. |
| October●●○○○ | 27–29 °C / 81–84 °F | 8–20 m | Some seasons open late this month; confirm sailings. |
| November●●●●○ | 27–29 °C / 81–84 °F | 10–25 m | Early-season trips resume when permitted. |
| December●●●●○ | 26–28 °C / 79–82 °F | 10–30 m | Conditions firm up; holiday charters fill first. |
Monthly figures confidence: Documented. Months without a row have no verified data — we would rather show a gap than invent one.
The dive sites (5)
| Site | Type | Depth | Level | Access | |
|---|---|---|---|---|---|
| Black Rock Oceanic mantas at close quarters, marbled rays stacked in the ledges… | Pinnacle | 5–40 m | Advanced | Liveaboard | |
| North Twin Armspan gorgonians on granite, raiding pelagics, dependable mid-trip quality | Reef | 8–35 m | Intermediate | Liveaboard | |
| Silvertip Bank (Burma Banks) Silvertip encounters with honest odds, oceanic-plateau atmosphere, true… | Seamount | 15–40 m | Advanced | Liveaboard | |
| South Twin Gardened granite boulders, easy conditions by Mergui standards, productive… | Reef | 8–30 m | Intermediate | Liveaboard | |
| Western Rocky The through-island tunnel with resting nurse sharks, elite macro walls… | Reef | 5–30 m | Advanced | Liveaboard |
Marine life you can plan around
Oceanic mantas and marbled rays at Black Rock, tawny nurse sharks in the tunnels, occasional whale sharks, schooling trevally and barracuda, cuttlefish and octopus, and rich macro from tigertail seahorses to harlequin shrimp; reef-shark numbers remain depleted from decades of fishing.
Getting there & staying
Getting there: Most divers fly to Ranong or drive from Phuket/Khao Lak, cross by longtail to Kawthaung for Myanmar immigration, and board there; some itineraries clear in and out on the same cruise from Thai ports. Domestic Myanmar routings have been unreliable since 2021.
Where to stay: You live aboard for the duration; there is no land-based dive infrastructure in the islands. A night in Ranong or Kawthaung bookends most trips.
Liveaboards: Liveaboards of 4-8 nights out of Kawthaung (often marketed from Khao Lak or Ranong) are the only practical access; northern routes to Black Rock and beyond need the longer itineraries.
Costs: Liveaboard-only economics: figure several hundred US dollars per night plus Myanmar entry, park, and permit fees typically totaling US$200-300 per person per trip, all arranged by the operator and subject to change.
Between dives: Deserted beaches, mangrove channels, and occasional encounters with Moken communities, approached respectfully and at the operator's discretion; otherwise the appeal is the emptiness itself.
Safety & practicalities
Hazards: Remoteness measured in days, strong currents and thermoclines at the pinnacles, overhead tunnels at Western Rocky, and an unstable political situation ashore; medical evacuation is slow and routes through Thailand.
This is expedition-tempo diving: carry a surface marker and audible signal, dive conservatively given the distance from care, and choose operators with strong safety records and current local knowledge. Review your government's Myanmar travel advisory before committing money.
Nearest recompression: No recompression facility serves the archipelago; casualties are evacuated toward Thai facilities in Phuket, many hours to a day away. Availability changes; emergencies go through EMS and DAN.