I have gone to Cozumel on a diving excursion..wonderful, friendly place!
Thailand someday....
So far, Ko Chiang is the prettiest place I've been in Thailand...Samui is beautiful, but a little westernized, Phuket might as well be Miami Beach London, and Ko Samet is nice but at least on the last trip the amenities could have been a bit better. But all the islands have wonderful snorkeling (SCUBA if your ears can handle it), and clear warm water...But I want to do Hua Hin, Ko Tao, Ko Phangan and several other places. I have land on a lake there for retirement.