South Twin Island - South Twin is a grassy, tree-topped granite island, 1 kilometre long, lying in an east-west direction approximately 10 nautical miles due west of Loughborough Island. There are 2 small bays on the south side. Topographically similar to the Similan Islands in Thailand, the island has deep, large rock structures forming gullies, long swim-through passages and overhangs.
In the shallows you'll find fine table corals hidden amongst the boulders and home to anthias and damsel fish. There are tiger cowries here and the elusive ribbon eel. Look carefully, as they are really very small, only showing maybe 3 centimetres above their holes in the sand. Male ribbon eels are black and females blue with bright yellow fins. Immature juveniles are all yellow. There are also colourful magnificent anemones and carpet anemones all being defended by plucky little anemone fish.
The deeper boulders are covered in brown disc anemones as well as purple soft corals, white bushy sea fans and crinoids. Acropora coral clings to the rocks in small patches. Various nudibranch species can be seen on the the rocks including twin magnificent and fried egg nudibranchs. Whitetip reef sharks can be seen under the boulders as can tawny nurse sharks. Solitary chevron barracuda can be seen patrolling the blue and large schools of rainbow runners often race by. Emperor angelfish and parrotfish are common as are schools of snappers, oriental sweetlips and fusiliers.
75 km from Kawthaung, South Twin is also a popular site for night dives as that's the time when you really get to see how colorful this reef is. The visibility is usually excellent and currents are usually gentle, making it a great dive site for divers of all skill levels.