Southeast Asia · Cambodia
Koh Rong & Koh Tang
Four hours offshore to Koh Tang, where the water finally clears
Photo: TomFitzhenry · CC BY-SA 4.0
Cambodia's diving is small and largely undeveloped, run out of Sihanoukville and the Koh Rong islands. The inshore sites are shallow, silty and best treated as macro. The reason to make the trip is Koh Tang, four hours offshore, where visibility opens to 20 m and hard coral survives in decent condition — the island is also where the Mayaguez incident, the last battle of the Vietnam War, was fought in 1975. Overnight trips are the only sensible way to reach it.
About diving in Koh Rong & Koh Tang
There are two quite different trips on offer. Inshore, day boats run from Sihanoukville or off the beaches on Koh Rong and Koh Rong Samloem for two shallow dives, often sharing the boat with a course group; the hops are short and the operation small, a handful of divers rather than a fleet. Going offshore means committing to an overnight trip that leaves in the evening or before first light, sleeps aboard and fits several dives into a long weekend.
Inshore the seabed is boulder, rubble and silt on gentle slopes, and the water carries sediment off the mainland, so you dive it looking down and close in rather than out into the blue. Offshore the structure improves: hard coral over boulder reef, shallow fringing sections around the islands and better-defined slopes to work along. Koh Prins is dived for wreckage lying on the seabed, broken up rather than any intact hull, and accounts of what the metal actually is do not agree.
It suits divers happy to trade polish for quiet: offshore sites can go days without a boat on them, guides know the rubble intimately, and nobody is queueing behind you. Tolerance for a long ride on a basic boat matters more than dive skill. Trips also depend on numbers, since offshore departures usually go only when enough divers sign up, so anyone travelling in the shoulder months should contact centres in advance rather than turn up assuming a boat will be going.
Best time to dive Koh Rong & Koh Tang
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Season | Prime | Prime | Prime | Prime | Good | Fair | Off-season | Off-season | Off-season | Good | Prime | Prime |
| Sea surface | 28°C82°F | 29°C84°F | 30°C86°F | 31°C88°F | 31°C88°F | 30°C86°F | 29°C84°F | 29°C84°F | 29°C84°F | 29°C84°F | 30°C86°F | 29°C84°F |
| Daytime high | 29°C84°F | 29°C84°F | 30°C86°F | 31°C88°F | 31°C88°F | 30°C86°F | 30°C86°F | 30°C86°F | 29°C84°F | 30°C86°F | 30°C86°F | 30°C86°F |
| Rain | 33 mm1.3 in | 22 mm0.9 in | 53 mm2.1 in | 102 mm4.0 in | 194 mm7.6 in | 311 mm12.2 in | 347 mm13.7 in | 295 mm11.6 in | 368 mm14.5 in | 228 mm9.0 in | 170 mm6.7 in | 56 mm2.2 in |
| Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|
| Prime | Prime | Prime | Prime | Good | Fair |
| Sea surface | |||||
| 28°C82°F | 29°C84°F | 30°C86°F | 31°C88°F | 31°C88°F | 30°C86°F |
| Daytime high | |||||
| 29°C84°F | 29°C84°F | 30°C86°F | 31°C88°F | 31°C88°F | 30°C86°F |
| Rain | |||||
| 33 mm1.3 in | 22 mm0.9 in | 53 mm2.1 in | 102 mm4.0 in | 194 mm7.6 in | 311 mm12.2 in |
| Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|
| Off-season | Off-season | Off-season | Good | Prime | Prime |
| Sea surface | |||||
| 29°C84°F | 29°C84°F | 29°C84°F | 29°C84°F | 30°C86°F | 29°C84°F |
| Daytime high | |||||
| 30°C86°F | 30°C86°F | 29°C84°F | 30°C86°F | 30°C86°F | 30°C86°F |
| Rain | |||||
| 347 mm13.7 in | 295 mm11.6 in | 368 mm14.5 in | 228 mm9.0 in | 170 mm6.7 in | 56 mm2.2 in |
2011–2025 averages. Sea surface: NOAA Coral Reef Watch, measured at the surface, so deeper water can run colder. Daytime high and rain: NASA POWER.
Oct–Jun is the season with Nov–Apr calmest; the south-west monsoon makes the offshore crossing impractical Jul–Sep.
Best months: January, February, March, April, November, December
Koh Rong & Koh Tang water temperature and weather by month
The sea surface runs from 28 °C (82 °F) in January to 31 °C (88 °F) in May. Most rain falls from May to October, peaking at about 370 mm (15 in) in September; it stays largely dry from December to April. Daytime highs sit around 30 °C (86 °F) all year. The coldest water here is about 27 °C (81 °F), so pack a 3 mm, or even a 2 mm, suit.
Dive types & marine life
Inshore is macro work: nudibranchs, frogfish, cuttlefish and octopus over the rubble, stingrays on the sand, and night dives the best time for the cephalopods. Turtles and schooling reef fish are more likely on the offshore islands, and October to May is the stretch when boats reliably get out to them — June is marginal, July to September off.
- Reef
- Muck & macro
- Night
- Wreck
- Coral garden
- Nudibranchs
- Macro critters
- Sea turtles
- Reef fish swarms
- Octopus & cuttlefish
- Frogfish
- Stingrays
Best dive sites in Koh Rong & Koh Tang
Reef
Seahorses and bamboo sharks on a slope that ends in sand at 16 m
Reef
Whale sharks reported in December and again in May
Two-metre cobia that come over to inspect divers
Reef
Stingrays in numbers at Sting Ray Alley, the deepest site here
How to get to Koh Rong & Koh Tang
Sihanoukville is the mainland base, reached by road from Phnom Penh, and ferries cross from its pier to Koh Rong and Koh Rong Samloem through the day. Centres work from both the town and the island beaches. Inshore diving is day-boat; Koh Tang is only realistic as an overnight or multi-day trip, run mainly between November and April, with October and May at the margins.
Photos from Koh Rong & Koh Tang
Kris Martyn · CC BY-SA 4.0
Luca Nebuloni · CC BY 2.0
Luca Nebuloni · CC BY 2.0
gbuschner · CC BY-SA 3.0
Dive videos
Diving trip in Koh Rong and Koh Tang (Cambodia) · EM & Y'ALL on YouTube
KOH RONG AND THANKS FOR ALL THE FISH | DIVING IN CAMBODIA · Ben Freely on YouTube
Photo credits
- White sand of Long Beach on Koh Rong curving along turquoise water under a blue sky by TomFitzhenry, CC BY-SA 4.0, via Wikimedia Commons
- Aerial view of a wooden pier reaching into turquoise water off Koh Rong Island by Kris Martyn, CC BY-SA 4.0, via Wikimedia Commons
- Traditional Khmer fishing boat with flag anchored in calm water near Koh Rong by Luca Nebuloni, CC BY 2.0, via Wikimedia Commons
- Jungle-covered rocky point meets a narrow sandy beach on the coast near Koh Rong by Luca Nebuloni, CC BY 2.0, via Wikimedia Commons
- Tree-lined shoreline with stilted huts seen from the water near Koh Rong by gbuschner, CC BY-SA 3.0, via Wikimedia Commons
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