Koh Tao is a small island about 70 kilometres north of Koh Samui — the world capital of scuba certification and one of the most spectacular underwater landscapes in the Gulf of Thailand. The island's name means "Turtle Island" in Thai, and the name fits: green sea turtles and hawksbills are regularly encountered here.

Marine Protection Status

The waters around Koh Tao fall within Thailand's system of marine protected areas. The Department of Marine and Coastal Resources (DMCR) actively monitors reefs, turtle nesting and compliance with ecological regulations. Several reefs around the island are closed to anchoring — boats must use mooring buoys.

Local dive centres participate in the Reef Check Thailand programme, regularly monitoring coral health and recording sightings of protected species. Koh Tao is one of the few Thai islands where the diving community has a real influence on local marine policy.

Best Dive Sites

Chumphon Pinnacle — an underwater rock formation stretching from 14 to 36 metres depth, north-west of the island. Famous for whale shark encounters (especially March to May), large fish schools and coral gardens. Consistently rated among the top five dive sites in Thailand.

Sail Rock (Hin Bai) — a solitary rock between Koh Tao and Koh Samui, dropping 40 metres to the seabed. Home to batfish, moray eels and the occasional reef shark. The highlight is the "chimney" — a vertical fissure that takes you from 20 metres back up to 5 metres.

Twins (Koh Nang Yuan North and South) — two submerged peaks off Koh Nang Yuan island. Soft corals, large reef fish and sea turtles. One of the most scenic shallow sites in the area.

Japanese Gardens — an extensive shallow coral-garden system (5–12 m) with exceptional fish diversity. One of the best sites for certification dives and snorkeling.

Mango Bay — Green Sea Turtles are encountered here almost daily. Shallow (to 15 m), excellent for beginners.

Snorkeling at Koh Nang Yuan

Koh Nang Yuan is three tiny islets connected by sand spits, a few hundred metres from Koh Tao. The water is so clear that corals are visible from the surface. Perfect for snorkeling without a dive tank. Entry fee: 100 THB (conservation charge; plastic and single-use bottles are prohibited on the island).

Getting There from Koh Samui

High-speed catamarans and ferries depart from Nathon pier (west coast) and Mae Nam. Main operators: Lomprayah and Seatran Discovery. Journey time: approximately 1.5–2 hours by fast boat. Routes run direct (Samui–Koh Tao) or via Koh Phangan (Samui–Koh Phangan–Koh Tao).

Dive centres on Samui organise day trips with early morning departure and evening return — convenient if you prefer not to stay overnight on Koh Tao.

Best Time to Visit

April through September offers the best diving conditions: high visibility and calm seas. October through December has slightly lower visibility but fewer tourists. January through March is also good, with March being the peak period for whale shark encounters at Chumphon Pinnacle.