Koh Tao is one of the world's busiest places to learn to scuba dive, and most beginners take a PADI or SSI Open Water course over three or four days. Before you pay, fill in the diver medical form, check that your insurance covers diving, and choose the school on safety rather than price alone.
An Open Water certification lets you dive with a buddy to 18 meters almost anywhere in the world. On Koh Tao the course is a normal holiday activity: you study in the mornings or online, practice skills in shallow water, then make four training dives from a boat. The island's dive schools compete hard for students, which keeps courses accessible but also means quality varies.
This page explains what the course involves, how to judge a school and what to sort out before you arrive. For the island itself, its beaches and where to stay, see our Koh Tao island guide.
Open Water Diver course at a glance (PADI figures)
- Duration
- "As little as 2–4 days"; three to four days is common
- Minimum age
- 10 (Junior Open Water Diver until 15)
- Water skills test
- Swim 200 m without aids, or 300 m with mask, fins and snorkel; float or tread water for 10 minutes
- Training dives
- Confined-water skill sessions, then four open-water dives, usually over two days
- Depth after certifying
- Up to 18 m (60 ft)
- Medical
- Diver Medical Participant Questionnaire; a "yes" answer may need a doctor's written approval
- Before flying
- At least 12 hours after a single dive, 18 hours after multiple dives (DAN guidance)
What the Open Water course actually involves
PADI describes three parts. First comes knowledge development: how pressure affects your body and your air, how to plan a dive and what the equipment does. You can do this as eLearning at home before the trip or in a classroom on the island. Doing it at home gives you more time in the water and less time studying on holiday.
Second, confined-water skills: in a pool or very sheltered shallow water you learn to breathe from the regulator, clear water from your mask, share air with a buddy and control your buoyancy. Third, four open-water dives, usually over two days, where you repeat the skills in the sea and start to actually look around.
SSI's Open Water Diver course follows a similar structure, and both certifications are recognized by dive centers worldwide. The choice between PADI and SSI matters much less than the choice of school and instructor. If you already know you will want to dive deeper later, PADI notes that the Advanced Open Water course is what opens sites below 18 meters.
Not sure yet? Try a single supervised dive
If you are not sure you will like breathing underwater, ask for a try-dive (PADI calls it Discover Scuba Diving). You dive with an instructor, shallow and closely supervised, without committing to the full course. Children aged eight and over can try scuba in a pool through programs such as PADI's Bubblemaker.
Do the medical form before you travel
Diving needs a basic level of health. PADI asks every student to complete the Diver Medical Participant Questionnaire, published by the Undersea and Hyperbaric Medical Society, and links to it from its course page. You answer yes or no to a list of questions about your health, past illnesses, operations and the medicines you take.
If you answer "yes" to any of the listed questions, you need a doctor's written approval before any in-water training. PADI is explicit that instructors, divemasters and dive shop staff are not doctors and should not be asked for medical advice. If you or your doctor have questions about fitness to dive, the Divers Alert Network (DAN), a non-profit diving safety organization, runs an information service.
A "yes" on the medical form is not something to talk your way around on the island. Download the form at home, and if you need a doctor's sign-off, get it from a doctor who knows your history before you fly. A school that tells you to just tick "no" is telling you something about its safety culture.
How to choose a dive school on Koh Tao
There are many dive schools on the island, mostly around Sairee Beach, Mae Haad and Chalok Baan Kao. We do not rank them, and nobody can guarantee that any particular school is safe. What you can do is ask the right questions. The UK Foreign Office warns that dive schools in Thailand "may have limited resources and do not always observe safety and maintenance standards", and its checklist is a good starting point.
- Credentials. Ask which agency the center is registered with, and check it on PADI's or SSI's own dive center locator. Ask to see your instructor's professional number.
- Group size. Ask how many students each instructor will have in the water. Smaller groups mean more attention when something goes wrong.
- Equipment. Look at the gear you will use. Regulators, hoses and buoyancy jackets should look maintained, not patched.
- Oxygen and first aid on the boat. The Foreign Office specifically says to make sure oxygen is available on board. Ask to see it.
- Emergency plan. Ask how a diver with a suspected injury would be brought ashore, which clinic or hospital they would go to, and how they would reach a hyperbaric (recompression) chamber.
- Language. Learning in your own language makes a real difference to safety. Ask whether an instructor can teach you in it, whether that is English, Chinese, German or another language.
- The quote in writing. Ask what the price includes (see below), and get it in a message or receipt.
Be wary of pressure. A good school answers these questions calmly. If staff are vague about oxygen or emergency plans, or rush you past the medical form, walk to the next one.
What drives the price of a course
We do not print course prices, because each school sets its own, they change with the season, and we could not find an official or independent price list to check them against. What we can tell you is how to compare quotes fairly, because headline prices on the island are often not like for like.
| Item | Question to ask |
|---|---|
| Course and training dives | Are all four open-water dives and all confined sessions included? |
| Learning materials | Is eLearning or the manual included, or bought separately from PADI or SSI? |
| Certification card | Is the card or eCard included? |
| Equipment | Is all rental gear included, including a wetsuit and dive computer? |
| Accommodation | Is a room included or discounted, and for how many nights? |
| Extra days | What happens, and what does it cost, if weather or an ear problem means you need another day? |
The cheapest quote is not necessarily bad value, and the most expensive is not necessarily safer. Compare what is included and how the school answered the safety questions above. Ask whether paying by card or QR code carries a surcharge. Our guide to daily costs in Thailand helps you budget the rest of the stay.
Insurance that actually covers diving
Many standard travel policies exclude scuba diving, or cover it only to a certain depth, or only once you are certified. Before you start the course, read your policy for three things: whether diving is covered at all, whether training dives are covered, and the maximum depth. The Foreign Office adds that some policies require dive instructors to hold certain qualifications, so check that condition against your school.
Specialist dive insurance, from organizations such as DAN, covers diving injuries and evacuation to a chamber. Whichever you choose, keep the emergency number in your phone. Our guide to travel insurance for Thailand covers medical cover in general, and our guide to hospitals in Thailand explains how private hospital billing works.
Staying safe during and after the course
Do not dive with a cold or blocked sinuses; equalizing the pressure in your ears becomes hard and painful, and pushing through it causes injuries. Tell your instructor about any pain, dizziness, numbness, unusual tiredness or breathing problems after a dive, even hours later. These can be signs of decompression illness, which needs oxygen and medical treatment quickly. In an emergency, call 1669 for an ambulance; our list of emergency numbers in Thailand has the others.
Plan your onward travel around your last dive. DAN's consensus guidance is a minimum surface interval of 12 hours before flying after a single no-decompression dive, and 18 hours after multiple dives per day or multiple days of diving. Since the Open Water course is several dives over several days, plan at least 18 hours between your last dive and your flight, and longer is better. The boat back to the mainland is fine; the flight is the issue. Our guide to getting to and from Koh Tao covers the boat and flight connections.
The sea has its own hazards. Box jellyfish have been recorded off Koh Tao, Koh Phangan and Koh Samui from July to October, according to Thai marine researchers; read our guide to jellyfish in Thailand. Do not touch coral or marine life. Researchers have recorded more than 130 species of hard coral around the island, and reefs damaged by fins and hands take years to recover.
When to learn: weather and sea conditions
Koh Tao sits in the Gulf of Thailand and follows the Gulf pattern rather than Phuket's. Thai Meteorological Department averages for nearby Koh Samui show October to December as the wettest months, with November the peak. Strong northeast winds in that period can cancel boats and churn up the water, so courses may take longer. The rest of the year usually has calmer seas, though no month is guaranteed. Our guide to the best time for the Thai islands compares the coasts.
Leave a spare day or two in your plans. A course that needs an extra day because of wind or an ear problem is common, and rushing to finish before a ferry is how people make poor decisions underwater. If you are combining diving with other islands, our Gulf island-hopping route fits a course into a longer trip.
Frequently asked questions
How long does it take to get an Open Water certification on Koh Tao?
PADI says the Open Water Diver course can be completed in as little as two to four days. Most schools on Koh Tao plan three or four days, and doing the theory as eLearning before you arrive shortens the time on the island. Allow a spare day for weather.
Do I need to be a strong swimmer to learn to dive?
You need to be comfortable in the water rather than fast. PADI's requirement is to swim 200 meters without aids, or 300 meters with mask, fins and snorkel, with no time limit, and to float or tread water for 10 minutes using any method you like.
Do I need a medical certificate to dive in Thailand?
Not automatically. You complete the Diver Medical Participant Questionnaire; if every answer is "no", you can usually start. If you answer "yes" to any question, you need written approval from a doctor before any in-water training. Get that at home where possible.
Does travel insurance cover scuba diving in Thailand?
Often only partly. Many policies exclude diving or limit it by depth or certification level, and some set conditions about the instructor's qualifications. Read the policy before your course, or buy specialist dive cover that includes treatment in a recompression chamber.
How long should I wait to fly after diving on Koh Tao?
The Divers Alert Network recommends at least 12 hours after a single no-decompression dive and at least 18 hours after multiple dives or several days of diving. An Open Water course falls in the second group, so allow 18 hours or more before your flight.
Sources
- PADI – Open Water Diver course: requirements, structure and medical form (checked October 2026)
- Divers Alert Network – Flying after diving (checked October 2026)
- UK Foreign Office – Thailand: safety and security (scuba diving, sea travel) (checked October 2026)
- SSI – Open Water Diver (checked October 2026)
- The Nation – Tourists warned of box jellyfish at Surat Thani's popular islands (2019) (checked October 2026)