Shark Bay, also known as Thian Og, is one of the best places on Koh Tao to see blacktip reef sharks and green sea turtles in their natural habitat. Sharks up to 2 meters long swim freely in shallow waters of 2-4 meters depth. The best time to spot them is early morning between 7-10am. The bay is protected and offers calm waters excellent for swimming and snorkeling.