I spent yesterday going to the Ang Thong national marine park. This area is a bunch of islands that are mostly uninhabited, and fairly small. The standard tour starts out somewhere on Ko Samui, and then you take a relaxing boat ride out a couple of hours to the archipelago of about 40 islands. Once you get there there is lots to do. We spent several hours kayaking thru the various grottoes and overhangs, finding several really decent snorkeling spots. One of the highlights of the trip is an island called Koh Mae Ko that features a closed lagoon connected to the sea by an underwater cave. Getting to it requires a bit of a hike thru some narrow and sharp rock passages, and a bunch of rickety bamboo ladders that have been worn down to almost nothing by the thousands of tourists that came before me.