Does it have to be Koh Samui? Take the slightly longer trip to Koh Phangan... if you look at a map of the Island, I'd recommend Haad Salat, top left... My Way Bungalows: beautiful, slow shelving cresent beach with a reef about 150 yards out with great snorkling. Selection of beach huts - some with hot water and aircon, some basic with just a fan. Great food and friendly owners/staff. And cheap!