South Twin
Depth is the range from the top of the site to its usual maximum; "recommended cert" is the mainstream-agency level operators usually ask for, not a legal rule. Currents and visibility change daily — treat everything here as planning ranges.
South Twin mirrors its northern partner at a lower volume: the same pale granite shouldering out of deep water, arranged into gardens rather than drama. Soft corals and carpets of zoanthids color the boulder tops, moray eels and octopus tenant the joints, and schooling snapper hold in the lee while barracuda hang higher like suspended cutlery. Sandy breaks between the rocks are worth slow inspection for partner gobies, flounder, and the occasional resting ray. Crews often assign it the first morning or the night dive, and its calm, spacious character suits both jobs well.
The moment you come for: Gardened granite boulders, easy conditions by Mergui standards, productive night option
Topography: Boulder gardens, coral heads, and sand patches around a granite islet
Current: Usually the gentler of the pair, with workable water most tides.
Know before you splash
Hazards: Standard remote-area caution; little else on a fair day.
Who you'll meet
Common Reef (Day) Octopus
Giant Moray Eel
Great Barracuda
Nudibranchs
Porcupinefish
For photographers
Wide angle: ★★★☆☆ · Macro: ★★★★☆ — editors' 1–5 rating of what this site gives each style of shooting