Average Depth: 15m (50ft)
Shark Island (Kong Sai Daeng)
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Maximum Depth: 28m (93ft)
It consists of two main rocks that are separated by a narrow channel which gives the island the look of a shark swimming on the surface, hence the name.
To the north, the rock walls drop down to 18-20m (60-67ft) and you'll find plenty of snappers, emperors and banner fish swimming around in large numbers.
If the current is right, you'll be carried around to the south where the coral garden starts and you'll find superb purple soft corals that look like cauliflower heads covering huge exposed areas of the rocks.
If you continue down deeper the site leads you down over several smaller pinnacles where you may be lucky to see whale sharks during the season.
On the west side of the island the depth is a pretty constant 5-7m (15-23ft) and is the best area for snorkelling and doing your safety stop after circumnavigating the island. Look out for pipefish and nudibranchs that graze on algae in the shallow depths. It is known for having the greatest diversity of marine life on Koh Tao.