Sanj, as Neuro says it's Google, not CR. Adsense used to be contextual, that is, ads for camera stuff would be shown on a site like this, but then interest based advertising (IBA) took over. If you search for something, you are then bombarded with ads for that subject wherever you go. I find it really creepy when ads follow you around from site to site, but apparently it works.
Back in my Thailand liveaboard diving days I had a couple of very good trips to the Similan Islands out of Khaolak with Sea Dragon - http://www.seadragondivecenter.com/
Things change and I don't know how the company compares these days, but my experience from several years ago was very good. The only problem nowadays is excess tourism and overdiving. The Thais have decided to shut a beach on Phi Phi island because the environment was being destroyed by tourists, and Boracay island in the Philippines will also be closed for six months for the same reason.
Although I live in Thailand, my diving days are over for various reasons - scarred retina, asthma, wife, kids, money, etc.
On my first trip to the Similans in 1996 there was hardly anyone there, but that all changed shortly afterwards. The attached shots from 1996 were taken with my old A1 and scanned in.
Have a good trip!