Koh Tao Diving: Courses, Dive Sites, Seasons and Choosing a School

Where Koh Tao is and how to get there

Koh Tao lies in the western Gulf of Thailand and belongs to Surat Thani Province. PADI places it in the Chumphon Archipelago and describes it as about two miles wide and five miles long (roughly 3 by 8 km). A 2022 survey by Ramkhamhaeng University researchers gives its area as 18.73 km². For other trips in the region, see our destination guides.

The nearest airports PADI lists are Chumphon (CJM) for domestic flights and Samui (USM) for international ones. The last leg is a boat to Mae Haad Pier, the island's main gateway, with daily ferries from Chumphon, Surat Thani, Koh Samui and Koh Phangan.

Lomprayah runs high-speed catamarans to Koh Tao from Thung Makham Noi Pier near Chumphon, from Koh Samui, Koh Phangan and Donsak pier near Surat Thani, and sells joint bus and boat tickets from Bangkok and from the Chumphon and Surat Thani airports. It gives its high-speed crossings as about 45-90 minutes, and says schedules vary. PADI also mentions a six-hour sleeper ferry from Chumphon for those who prefer to travel overnight.

Why so many people learn to dive on Koh Tao

Koh Tao certifies a very large number of new divers, but we could not find a total for the island published by PADI or a Thai authority, so we do not quote one. What PADI has published are milestones for single schools. Ban's Diving Resort, which started diving on the island in 1993, passed 150,000 PADI certifications in May 2014. Crystal Dive reached 100,000 certifications in 2017. A 2024 PADI article calls the island one of the most popular places to train as a dive professional, and a 2015 James Cook University study describes it as a global scuba diving hotspot.

The water suits training. Black Turtle Dive calls Aow Leuk, a bay on the south-east coast with a maximum depth of 15 m, a critical year-round training site, and Big Blue Diving says Japanese Gardens off Koh Nang Yuan starts at 2-3 m with little current most of the year. SSI notes that the island has numerous dive centres for different budgets.

What a Koh Tao Open Water course looks like

Plan on three days if you finish the theory online before you arrive. Black Turtle Dive's published PADI schedule is a useful example. Day one is paperwork and five confined water sessions in a pool. Day two is a quick review, a swim test and open water dives one and two. Day three is open water dives three and four. The training dives are at Mango Bay, Japanese Gardens, Twins and Aow Leuk bay, with at most four students per instructor. PADI's own page says you can learn in as little as 2-4 days.

The core is the same across agencies. SSI's Open Water Diver has a minimum age of 10, a swim assessment and survival float, and four open water dives, and certifies you to 18 m (60 ft). CMAS One Star asks for a minimum age of 14, a 200 m swim and four open water dives of at least 20 minutes each at 5-20 m.

Prices and inclusions differ between schools. We compared listed Open Water prices around the world, a Koh Tao centre included, in how much a scuba diving course costs. If Chumphon Pinnacle or the Sattakut wreck is on your list, plan an Advanced course as well: SSI rates both as advanced sites at 18-30 m, deeper than the Open Water limit.

How to choose a dive school on Koh Tao

Ask first how many students each instructor takes. CMAS caps One Star open water dives at four candidates per instructor, and Black Turtle Dive and Big Blue Diving both publish a maximum of four students per instructor. Other agencies' standards allow larger groups, and our guide on how to choose a dive centre lists the published ratios for each. Get the number for your own dates, not the website figure.

Then work through the rest before you pay. Most of these points come from Big Blue Diving's own checklist for Koh Tao:

• Which agency issues the card (PADI, SSI or CMAS), and is the centre an authorised training centre for it?
• Who will teach you? A centre that can name your instructor before you book is a good sign.
• Where do the confined water sessions happen: a pool, or shallow water where students can stand?
• Is emergency oxygen carried on every boat, is there a written emergency action plan, and are staff trained to give oxygen and first aid?
• What does the price cover: rental gear, certification fees, boat transport and a dive computer?
• Red flags: no medical questionnaire, no swim test, a group larger than you were quoted, skills rushed to fit a schedule, or promises of guaranteed whale shark encounters.

Koh Tao dive sites by depth and level

Koh Tao diving splits into shallow bays used for training and offshore pinnacles that ask for more experience. The depths and levels below are what SSI and local operators publish. They do not always agree, so each figure carries its source.

Chumphon Pinnacle, northwest of the island, is one of the pinnacles where whale sharks are reported. Sail Rock sits about halfway between Koh Tao and Koh Phangan and has a vertical chimney. The HTMS Sattakut is a 48 m former US Navy landing craft, sunk as an artificial reef on 18 June 2011 about 1 km west of Koh Tao. Its keel rests at 27-30 m and the top of the mast is at 18 m, so Big Blue Diving recommends Advanced Open Water for it.

Best time to dive Koh Tao, visibility and water temperature

March to September is the main season. SSI gives those months the best conditions and names October to December as the monsoon, with rain and rough seas. PADI says visibility reaches up to 30 m in July-September, SSI says it often exceeds 20 m (66 ft), and PADI puts the water at around 29°C (84°F).

The rain on this coast comes later than in most of Thailand. A 2002 JICA study of the Gulf coast south of Koh Tao describes the northeast monsoon as running between mid-October and mid-February, and notes that abundant rain continues on the east coast of southern Thailand until the end of the year. In its study area, river flows peak in November and December, and the highest waves came between October and January. If you book a course in those months, keep spare days for cancelled boats.

Whale sharks are seasonal and never guaranteed. PADI says they are most commonly seen in April and May, and SSI says March to April. The 2022 Ramkhamhaeng University survey reports frequent sightings at Chumphon Pinnacle (Hin Chumphon) and another pinnacle, Hin Khao, in March-April and again in August-October. All three agree on spring; the second window is worth knowing if you travel in the northern summer.

Reef health and the rules divers follow on Koh Tao

The island's busiest reefs show the cost of heavy use. Lamb and colleagues surveyed 10,499 corals around Koh Tao (Biological Conservation, 2014): 79% were healthy at low use sites against 45% at high use sites, and coral disease was three times as common where tourism was heaviest. A follow-up by Hein and colleagues (2015) found that sites with a history of heavy use still had less hard coral and more disease. Divers are not the only cause. Weterings (2011) found commercial snorkel trips more damaging than divers, and reported that almost half the island's rainforest had been lost, sending sediment onto the reefs.

The offshore pinnacles are in better shape. The 2022 survey measured 42.8% live coral cover at Chumphon Pinnacle, with 27 species of reef-building coral, and says the pinnacles remain in good condition despite bleaching events in 1998 and 2010.

Rules have grown out of local action:

• Zoning: New Heaven Reef Conservation Program records a first set of rules in 1994, with a 3 km trawling exclusion zone and a 1 by 5 km no fishing area off Sairee Beach, and a 2012 coastal management plan drawn up in meetings supported by the Department of Marine and Coastal Resources (DMCR).
• DMCR orders: in 2018 the DMCR ordered protective measures for Koh Tao, Koh Samui and Koh Phangan for two years. Boats must tie to mooring buoys instead of anchoring on coral, feeding marine animals is banned and sea walking is prohibited, The Nation reported. Ask your centre which measures are in force now.
• Sunscreen: since 2021 Thailand bans sunscreens containing oxybenzone, octinoxate, 4-methylbenzylidene camphor (4MBC) or butylparaben in its marine national parks, with fines up to 100,000 baht. The ban is written for national parks, but a mineral sunscreen or a rash guard is a sensible default on any reef trip.
• Restoration: New Heaven lists coral nurseries, artificial reefs and giant clam nurseries among the island's projects, and Crystal Dive set up a separate conservation department, Eco Koh Tao.

Recompression chamber, insurance and flying out

Koh Tao has its own chamber. The SSS Recompression Chamber Network lists a 24-hour chamber and medical team on the island, run by Hyperbaric Services of Thailand, as its Gulf coast site, with an emergency line on +66 81 081 9777. Black Turtle Dive says the island's government hospital can evacuate patients by speedboat or helicopter to larger hospitals on Koh Samui and in Chumphon. In a life-threatening emergency DAN says to call local emergency services first, then its 24-hour hotline on +1-919-684-9111.

Check that your policy covers diving and evacuation before the course starts. Black Turtle Dive advises non-Thai visitors to arrive with full health and medical insurance, and our guide to what dive insurance covers explains the difference between travel and dive-specific cover.

Leaving the island means a ferry before any flight from Samui or Chumphon. DAN recommends at least 12 hours after a single no-decompression dive and at least 18 hours after multi-day repetitive diving, which is what a course followed by fun dives adds up to. Enter your last dive in our flying after diving calculator before you book the ferry and the flight.