Chalok Ban Kao is Koh Tao's southern bay, calmer and quieter than Sairee but still with plenty of services. The bay is shallow and well-sheltered, making it good for swimming even when the west coast is choppy. Several dive schools operate from here, and the atmosphere is noticeably more relaxed than the main tourist strip.
The southern headland above Chalok Ban Kao has a viewpoint that many consider the best on the island — a short steep hike rewards you with views over the bay, the offshore islands, and on a clear day all the way to Koh Phangan to the south. This is also the area to head for if you want to do yoga, take a cooking class, or find the kind of guesthouse where people stay for a week and forget to leave.