Koh Rong

Sihanoukville · Sihanoukville Province · Cambodia

Koh Rong is Cambodia's largest island and its most promising dive destination, a mountainous jungle-clad landmass rising from the Gulf of Thailand roughly twenty-five kilometres from Sihanoukville. For years it was known primarily as a backpacker beach haven, but a growing community of dive operators has begun revealing an underwater world that, while modest compared to the Coral Triangle, offers genuine surprises and a refreshing absence of the crowds that plague similar destinations in neighbouring Thailand. The diving at Koh Rong centres on rocky outcrops and coral formations scattered around the island's coastline, particularly along the less-developed western and northern shores. These sites feature hard and soft corals growing on granite boulders at depths of five to eighteen metres, creating a habitat that attracts a surprisingly diverse community of marine life. Seahorses — both the thorny and common varieties — are a signature find, clinging to gorgonians and sponges at several sites. Pipefish, nudibranchs in impressive variety, and blue-spotted stingrays round out the macro attractions, making Koh Rong a quiet macro paradise. The fish life benefits from Cambodia's relatively low fishing pressure compared to the rest of the Gulf of Thailand. Schools of batfish cruise the water column, barracuda hang in lazy formations, and cuttlefish display their chromatic genius against the reef backdrop. Moray eels inhabit the boulder crevices, lionfish drift under overhangs, and the occasional bamboo shark rests on sandy bottoms during early morning dives. The reef system is young and recovering from past dynamite fishing, but the trajectory is positive, and new coral growth is visible on many sites. Above water, Koh Rong is famous for its bioluminescent plankton, which light up the sheltered bays in electric blue on dark nights — a phenomenon that pairs memorably with night diving. The island's development is still at an early stage, preserving a wild, unhurried atmosphere that will appeal to divers tired of production-line dive tourism. Getting there takes about forty-five minutes by speedboat from Sihanoukville, and the handful of dive centres offer certification courses and guided dives at prices well below regional averages.