Mergui Archipelago

Diving here is a boat trip in the fullest sense. Immigration is cleared at Kawthaung, you board for the better part of a week, and everything afterwards happens from the mothership and its tenders: no dive shops, no walking away from a bad day, no changing your mind on day three. Operators plan around long overnight steams between island groups and fit in three or four dives a day where the anchorage allows. Itineraries are usually rewritten mid-trip around wind and swell rather than published in advance.

The rock sets up two different kinds of dive. The islands are largely granite, and the same stone carries on underwater as stacked boulders, gullies and gaps wide enough to swim, with soft coral where water moves and sponge in the shade. Away from land, isolated pinnacles rise out of open water and behave like small mountains: current splits around them and fish stack up on the exposed side. The offshore banks sit far from any island, so a dive there begins and ends in blue, and the steam out to them is long enough that not every itinerary includes them.

What the region trades away is predictability. The water is often green rather than clear, and the plankton behind that is also what feeds the fish, so some of the better animal encounters come on the least photogenic days. Inshore, silty bays with rubble and scattered coral heads are the macro ground, and where night dives get scheduled when the outer sites are unworkable. Sites rarely have another boat on them, which also means nobody has been out to check conditions ahead of you.

That suits divers already comfortable in moving water, with descents down a line into blue and the occasional negative entry when a pinnacle has to be hit first time. Depth is not the problem, since most of the diving falls in the 12 to 30 metre band. Distance is: the nearest recompression facilities are back in Thailand, and reaching them means steaming to Kawthaung first. Anyone who needs dependable visibility, easy exits or a fixed schedule will be happier elsewhere.