Koh Rong tide times

Koh Rong is Cambodia's second-largest island, roughly 78 km² of forested volcanic terrain rising to 235 m at its central peak, positioned 25 km west of Sihanoukville across open Gulf of Thailand water. The island holds several distinct coastal environments: the southeast, where the ferry pier and the village of Koh Tuch concentrate most visitor services, is a sheltered bay with shallow sandy approaches; the west coast from Village 4 (Koh Rong Village) northward runs 7 km of largely undeveloped beach that is among the finest in Southeast Asia; and the northern coast and the mangrove-fringed channels on the island's eastern side are shallow and tide-sensitive.

The tidal regime at Koh Rong mirrors Sihanoukville's mixed diurnal Gulf pattern. The island sits far enough offshore to experience slightly more open-water conditions than the mainland bays, but the fundamental Gulf of Thailand tidal character applies: one dominant rise and fall per day through much of the monsoon season (June to September), compressing to a range of 0.6 to 0.8 m on the most diurnal days, and two recognisable tidal cycles per day in the November-to-February season with spring ranges approaching 1.0 to 1.2 m. The tidal flats around the Koh Tuch ferry pier area on the southeast coast partially dry at spring low water, affecting access for small wooden fishing boats and the shallow-draft water taxis that serve beach resorts on the northern side of the village bay.

The bioluminescent plankton phenomenon in the shallow bays of Koh Rong — Pyrodinium bahamense, which emits blue-green light when physically disturbed — is one of the island's most frequently cited attractions. The phenomenon is best observed by wading into calm, shallow water at night and disturbing the surface. It is not tide-stage dependent in the sense that the plankton is present at all tidal stages; however, calm nights with little swell and minimal cloud cover provide the best conditions, and the new moon period gives the darkest skies and makes the bioluminescence most visually striking against the dark water.

The west coast beaches from Village 4 northward represent some of the least-developed beach stretches in the Gulf of Thailand region. Access is on foot from the village via jungle trail, by boat, or by a rough track that connects to the east coast road. The shallow gradient of the western beach means the waterline shifts 10 to 20 m between spring high and low water on the more semidiurnal days. On the most diurnal days the apparent change is smaller because the total daily range is compressed.

Snorkelling and diving off Koh Rong centres on the reef patches around the southern tip, around the satellite islets to the east (Koh Toch Loch), and at dedicated dive sites accessed by liveaboard or day-boat. Visibility depends on sea state, sedimentation from river runoff after rain, and tidal current stage; the slack-water windows around the predicted high and low give the clearest conditions at reef sites.

The island's only road connects Koh Tuch on the southeast coast to the north-facing beaches; most of the western coast is accessible only by boat or the jungle trail. In the dry season (November through April) the trail is passable; in the wet season it can be slippery and poorly marked. Fresh water on Koh Rong comes from springs and small streams; the island has no mains water system and resorts manage their own supply. Electricity on the outer beaches is typically solar or generator. These practical facts shape the character of the island as much as any tidal or weather consideration. Predictions on this page come from Open-Meteo Marine, a gridded global ocean model; accuracy is typically within plus or minus 45 minutes on timing and 0.2 to 0.3 m on height. The Department of Meteorology, Hydrology and Hydrography of Cambodia (DMHH) is the national authority for tide data in Cambodian waters.