Whale sharks off Koh Tao: when and where you can encounter them

Before Koh Tao, whale sharks arrive at the dive sites in the open water. Divers log them most frequently at the Chumphon Pinnacle, the Southwest Pinnacle, and Sail Rock. There is no fixed season, and the dive operators mention different months. March to May and September to October are the most common. An encounter is never guaranteed, even during the best weeks.

The months with the best chances

Big Blue Diving calls March to May the best time at the Chumphon Pinnacle and the Southwest Pinnacle, with regular sightings in September and October at Sail Rock, the Chumphon Pinnacle, and Shark Island. Three other operators also see the peak from March to May, while Chalok Reef Divers calls March to June the best time for the Southwest Pinnacle. The president of the Koh Tao Tourism Association, on the other hand, calls June to September the high season.

The SSI app logbooks show a different picture. By October 2026, divers have logged 7,794 whale sharks at 17 of the 72 sites in the Gulf. On average, there is one entry for every 200 dives, and around 80 in September. No other month is so clearly above average.

Month	Big Blue Diving	Tourism Association	Logbooks (SSI)
March to May	best time
June to August		high season
September	regular	high season	most entries
October	regular

Whale sharks eat plankton. When plankton blooms reduce visibility at the Chumphon Pinnacle to 10 to 15 m, whale sharks often come after Big Blue. According to Crystal Dive, the water is clearer from March to May, with visibility of 15 to 30 m. From late October, the northeast monsoon blows. At Sail Rock, trips are then canceled in October and November, and Big Blue has both pinnacles on the schedule until the end of November, depending on the weather after that.

The three sites

Chumphon Pinnacle

The pinnacle is located 45 minutes northwest of Koh Tao in the open Gulf, with the top at around 14 m and the bottom at 36 to 40 m. Above the anemone gardens are schools of barracuda, batfish, and trevally. Most dive operators require Advanced Open Water. With the basic certificate, Big Blue takes you to the top. The current ranges from none to strong and can sweep you away from the boat, so a buoy is essential. Silent Divers takes around 90 minutes from Koh Samui.

Southwest Pinnacle

Seven granite peaks stand here on the sand, the highest reaching to around 5 m below the surface, with the bottom at around 30 m. The boat takes around 45 minutes from Sairee Beach. The dive operators consider the site suitable from Advanced Open Water and call the current noticeable to strong. At the Secret Pinnacle, five minutes from the main pinnacle, the zero time is short.

Sail Rock

The rock lies between Koh Tao and Koh Phangan and drops to around 40 m. From Chaloklum on Koh Phangan and from Koh Samui, it takes around one hour, and from Koh Tao up to two hours; Big Blue sails there about every three days. With Open Water, you can dive here to 18 m. Below 25 m, according to Silent Divers, there is often a thermocline.

How to behave during an encounter

The whale shark has been listed as Preserved Wildlife under the Wildlife Conservation and Protection Act in Thailand since 2019, and Thailand's 2025 Red List classifies it as critically endangered. Anyone who hunts it, which also includes pursuing and harassing it, risks 3 to 15 years in prison or 300,000 to 1.5 million baht. The marine authority DMCR asks divers to hover calmly, neither pursue nor touch the whale shark, nor block its path. A DNP national park calls for a distance of 3 to 4 m and no flash. Boats must keep a distance of at least 20 m according to the DMCR and travel at less than 2 knots over the final 50 m.

So stay at your depth and let the whale shark come. Otherwise, you will easily drift away from the group in the current at the pinnacle.

When to plan your trip

If you want to increase your chances, plan the trip between March and May or in September and October, and dive several times at the pinnacles and at Sail Rock during this time. The two pinnacles are easiest to reach from Koh Tao, and Sail Rock from Koh Phangan, where Sail Rock Divers sails every day. What to expect in terms of water, rain, and wind each month is shown in the Travel Season by Month table in the magazine. Which island is right for you is compared in the article Koh Tao, Koh Phangan, or Koh Samui?.

Portraits of all three sites with entry, depth, and current are in the booklet Dive Sites on Koh Tao and Koh Samui and in the full magazine.