Maya Bay is beautiful, cristal clear water the sand like flour..amazing! Take a walk in the "jungle", its very quiet and amazing! Important thing: take the "avoid the crowed" tour (or hire a privet boat), which starts at 6AM from the pier! This way will be only 1-2 longtail boats at the bay when you arrive..!! We spent 1,5 hour here, and when we departed there were no space to swim or enjoy the view - at least 25-30 speedboats/longtail boats were docking at the bay (its mean 15-25 pay per boat..)!
So definitely a must see - but only in the early morning!