Not a detailed trip report as im way too tired, more of a few general observations.
Ive just done 6 days on a liveaboard to the Mergui archipelago in Myanmar.
Generally this is a fairly remote and mainly uninhabited island chain in the andaman directly north of Thailand (Richelieu, Surins) and obviously is a LOT quieter.
There are some "established" dive locations there but not many, most of it is just jump-in-and-see type diving.
First thing that struck me were the currents, swirling and occasionally strong (neaps helped). The other thing was the amazing colour and abundance of soft corals - every rock on the westward side is covered in vastly different colour soft corals.
As the whole area in limestone some sites have swim-throughs, tunnels and even caves (western rocky for example has a tunnel right through it). There seem to be a large number of smaller fish life (fusiliers and the usual suspects), some bigger trevally and barracuda but we didnt see any of the real big stuff.
On the macro side of things, tons of nudibranchs (which i generally ignore), loads of seahorses, ghost pipefish, mantis shrimp and so on.
You're unlikely to see any other boats at all except fishing boats (more on that shortly) and the chances of seeing any other dive groups underwater are pretty much zero unlike the Thailand dive sites just to the south.
On the more negative things, the visibility was relatively low. Apparently way lower than normal the first 3 days (5m of dark, green, UK style feel) but did get better the last 2 days to a blueish 15m or so. The water was also 2c colder than thailand (27c) so we froze our arses off.
As its not a marine park of any sort we did see fishing net and line on quite a few of the sites, no evidence of dynamite but something to be aware of and might explain the lack of big stuff. That said maybe we just weren't lucky or right place/right time for anything big or vis. Hard to tell until i go back.
The main downside is my camera flooded in the rinse tank on Christmas morning when the dome detached from the housing. The terrible ikelite "design" of no screw, no lock, no bayonet fitting finally undid me like ive seen it do to so many before. Im guessing the water was slightly salty as the camera and the lens are both totally and utterly dead (70D and 10-17) but sh*t happens. Riding my luck with an ikelite housing in particular anyway so now im looking at upgrading.
Top side the scenery is stunning, towering limestone cliffs covered in jungle, some tropical beaches with nobody there and so on.
A few photos:-
North Rock (Frog Rock) by Richard Whitcombe, on Flickr
Christmas. Deserted tropical beach on Hlaing Gu Island (Myanmar) by Richard Whitcombe, on Flickr
Octopus mating - with an audience by Richard Whitcombe, on Flickr
Western Rocky cave by Richard Whitcombe, on Flickr
Ridiculously colourful soft corals,"Frog Rock" (North Rock, Myanmar) by Richard Whitcombe, on Flickr
Well hidden Scorpionfish by Richard Whitcombe, on Flickr
Big seahorse (Western Rocky) by Richard Whitcombe, on Flickr
Colour everywhere by Richard Whitcombe, on Flickr