Cambodia
Best overall months to dive: Jan, Feb, Mar, Apr, Nov, Dec
Cambodia's diving is confined to the Gulf of Thailand off the southwest coast, centred on the Koh Rong archipelago in Sihanoukville province. It is a shallow, silty, river-influenced sea: visibility inshore is commonly 5-10m, coral cover is patchy, and decades of bottom trawling have thinned the marine life. There is no reliable big-animal diving, and most divers here are backpackers taking a cheap Open Water course rather than travellers who came for the reefs. Note that Cambodia's well-known Irrawaddy dolphins are a freshwater population on the Mekong at Kratie, not a dive.