The Similan Islands are a chain of islands classified as a national park off the West Coast of Thailand (Phuket is the closest city). It takes about an hour and a half to get there by speedboat. On the way there, our host was kind enough to supply anti-nausea pills as we were basically out in open water for the whole trip (and this was a calm day; apparently they couldn't even go out the few previous days due to rough weather). We saw some whales, which led to some poor photographs of shapes in water, but Bryce managed a video that turned out pretty well.
Our trip was 3 days/2 nights and the primary activity was snorkeling. I've never been snorkeling before, but this was an amazing introduction. Even before arriving at the camp site, we squeezed in some snorkeling off the speed boat. I haven't been in salt water for a while, but it didn't really remind me of BC's ocean anyway: the water is too clear and too warm for that.
After having some lunch and finding our tents, it was back out on the boat for more snorkeling. The second spot was where I discovered (with Bryce's warning) the little jellyfish and/or jellyfish eggs that sting you as you go along. They aren't bad even though the sting lasts for several minutes. I fared much worse on land with the many mosquitoes and other bugs that attacked at sunset when we returned.
The middle day had meals on the boat (all seafood, really good meals all included in the trip, but too bad for Bryce who can't stand the stuff) and lots of snorkeling. By the end, I had seen all kinds of fish, huge schools of them. Very impressive. And I was exhausted. Not surprising, as I have been on a regular drinking schedule as opposed to any kind of exercise schedule for the past month(s). I also managed to develop quite a sun burn, which I guess was bound to happen here at some point, so time to get it over with.
By the trip home on the third day, I was pretty wiped after all the sun and swimming. The tents had not been the ultimate for sleeping (it rained the second night, water getting into the tents, plus partying nearby late into the night), so it was a real treat to reclaim our air-con room in Phuket. Anyway, I would recommend this trip if you are in or near Phuket, as the snorkeling (and maybe the diving, people were up to that as well) are really something to see. You might want to try the 2 day/1 night, though, and if things are going well they might offer a cheap extension of a night or two while you are out there (they did for us, anyway).