Thanks for the reply and info. The Surin Is. look appealing for many reasons, so I think we'll just go and explore for ourselves. Couldn't find many potential snorkeling destinations in SE Asia at that time of the year (NE monsoon). I'm fairly adept at free diving / deeper-water snorkeling too, so that might open up some sites, but I'm going with my sister who doesn't Scuba and just likes to float at the surface.