Oh my goodness, go to KOH LIPE! I've been to Phi Phi and Phuket and all that but it's just very very crowded. Lipe has the clearest water I have ever ever ever seen in my entire life. Stay on the "sunrise beach" side, it's less crowded (not that there are too many crowds anyway). I went a few years ago and I hear that it's no longer a secret, so it could be a little more crowded now, but it's incredible. We stayed at Gypsy resort right on the water. I couldn't imagine a more idyllic place than Koh Lipe. If you want things to do other than snorkelling, laying on the beach and eating, it may not be the place for you, however if you want to do absolutely nothing and relax in a hammock reading, done and done!