A friend and I are planning a trip to Thailand in late February/early March.
My top priority is to go snorkeling. After reading through the Forum, my sense is that the best snorkeling is on the Similan & Surin Islands. My question is about accommodations and am trying to decide whether to stay in a bungalow on the islands or in a live-aboard (don’t want to do 2-3 hour boat rides every day). How basic are the accommodations? Do either bungalows and live-aboards have their own bathrooms? Air con? Any recommendations one-way or the other? Will I need to make reservations in advance or just show up? Typically, how many people per boat on a live-aboard?
I’ve never gone scuba diving, so my second priority is to do what someone post referred to as “ try dive”. What is that? Will most/all dive shops offer that?
Finally, of the snorkeling options closer to the mainland (on the Andaman side), which are the best? Phuket? Phi Phi? Any others?
Thanks.

On both the Similan and Surin Islands there are basic tents and Bungalows run by the goverment. On the Similans there are Aircon bungalows for 2000 Baht a night. They have a good view but have those infamous superhard Thai mattresses. On Both Islands they have restaurants, though the restaurant on the Surins is pretty good! The Bungalows have shared bathrooms (except the 2000 baht rooms)
As for visiting the islands, you seem to have been misinformed. The boat ride is about 1 hour to 75 minutes. The age of 3 hour boat rides is long past. You can easily visit the islands each day and sleep in your hotel each night.
There is a snorkeling liveaboard run by poseidon that does some of this islands as well.
As for try diving, all shops do that here. You can do one as part of a snorkeling trip to the Similans, which is a great option. A try Dive, is either a brief spin around the water, with you not controlling anything, and the instructor doing that. You get a good feel for the basics and see how things work. There is also a full day course that involves some more basic orientation to diving and the skills, and you should get a full dive as well. Either way, you can do these courses very easily. Be prepared to stick around and do your whole Open Water course though!

Thanks very much for your response - that's really helpful. Couple more questions - You said the boat ride to the island is 60-75 minutes? Is that from Phuket or from Khao Lak? If I'm staying in Phuket, would you take the boat right from there, or go by road to Khao Lak and then by boat to the Similan Islands? How about to the Surins?

I found on another forum talking about a place in Khao Lak called Poseidon. I went to look at the site and it is very interesting indeed. The website is Poseidon. The accommodation is very basic. They do the snorkelling liveaboard which is very interesting.
I am diver so I will be keen on the trip for diving only which they can also provide. They have the course for diving that you can attend. Check out the website pics of the accommodation, I think that this is rare to find in Thailand at the moment and indeed it is an ideal. I have never tried what you called "Tried Dive" but i guess that you will have to learn this on a shallow place or in the swimming pool. I think that if you have time, please go ahead unless you have any kinds of phobia to stop you enjoy diving.
Most of the liveabord does not have bathroom/shower room in the bedroom unless it is a private yacht or one of the most expensive boat.
Cheers,