As the beach in Karon wasn't very nice, we went on a few whole day excursions to other islands to enjoy white sandy beaches and swimming in crystal clear water. Raya Island is highly recommended by us as it's very close - transfer from the hotel it's 15-20 minutes from Karon, then half on hour on a motor boat and you are on a wonderful beach. It's true that most of the beaches are very crowded and motor boats spoil the view, but it's still very nice. You can rent a sunbed and stay under and umbrella, or - as we did - spend most time in the water enjoying swimming or explore the island (on the way to a view point you can see big iguanas). As always on such excursions, soft drinks, fresh fruits and lunch are included in price.
The excursion itself was cheap - only 1000 Bht (the price stated in leaflets is 2000 Bht, but you can negotiate.:)