Koh Tao's Offshore Pinnacles: What You'll See at Sail Rock, Chumphon and Southwest

Key takeaways

• Koh Tao has three offshore pinnacles: Chumphon Pinnacle, Southwest Pinnacle and Sail Rock. They are where the big fish are.
• Southwest and Sail Rock are great for Open Water divers — the top of Southwest is only 5 m down and Sail Rock breaks the surface. Chumphon’s top sits at 14 m, so it is a step up.
• Whale sharks peak March–May and September–October, but in 2026 we’ve been seeing them at other times of year too.
• Barracuda and trevally are there all year; the trick is to look out into the blue, not at the rock.
• We dive Chumphon and Southwest on the morning boat and run Sail Rock as a day trip every Friday.

Most people learn to dive on Koh Tao in the bays. The pinnacles are where you go once you have — three granite peaks standing alone in open water, each wrapped in anemones and surrounded by fish that have nowhere else to gather. This is the guide to read the night before you dive them: what each one is like, how deep it goes, what you will see and where to put yourself to see it. For each species there is a longer page; this one is about the sites.

The three pinnacles at a glance

	Chumphon Pinnacle	Southwest Pinnacle	Sail Rock
Where	North-west of Koh Tao, open water	South-west of Koh Tao, open water	Between Koh Tao and Koh Phangan
Top of the rock	14 m	5 m	Breaks the surface
Bottom	30+ m	30 m	30+ m
Who can dive it	Open Water, but more challenging — you start at 14 m	Open Water	Open Water
Signature	Anemone fields, whale sharks, big schools	A cluster of peaks, groupers and snappers in the blue	The vertical chimney swim-through
How we get there	Morning boat from Sairee Beach, ~6:45	Morning boat from Sairee Beach, ~6:45	Friday day trip

Chumphon Pinnacle

Koh Tao’s signature deep site. The main pinnacle rises from the sand to a plateau at 14 metres, with smaller peaks around it and a carpet of magnificent anemones on top. Because the top is already at 14 m, the whole dive happens in the 14–30 m band, which is why we call it the more challenging of the three for a new Open Water diver: there is no shallow part to retreat to, and the current can run.

What you’ll see. Barracuda in slow chevron schools a few metres off the rock; giant and bluefin trevally hunting through the fusiliers over the plateau; batfish around the pinnacle’s edges; groupers in the anemone fields; and, in season, whale sharks.

Where to position yourself. Drop down the mooring line, settle on the up-current side of the plateau and face out. The schools sit side-on to the current, and the trevally come to you. Spend the second half of the dive shallower, around the top of the pinnacle, which is also where a whale shark will pass if one is about.

Southwest Pinnacle

A cluster of submerged peaks rather than one rock, with the tallest reaching up to just 5 metres below the surface. That makes it a great site for Open Water divers: you can do the whole dive between 5 and 18 metres and still be in the middle of everything, while Advanced divers drop to the sand at 30 m around the base.

What you’ll see. Big schools circling the peaks in the blue — snappers, fusiliers, barracuda; groupers and moray eels in the cracks between the peaks; anemones and their clownfish on every top; and whale sharks on their day.

Where to position yourself. Swim the gaps between the peaks rather than around the outside — that is where the eels and groupers are — then finish the dive hanging off the shallowest peak at 5–10 m with the school turning around you. Keep your eyes on the blue during the safety stop.

Sail Rock

The Gulf of Thailand’s most famous dive. Sail Rock stands out of the water between Koh Tao and Koh Phangan and drops to over 30 metres, and because it breaks the surface there is something to see at every depth — which is why it works for Open Water divers as well as the deep crowd. The vertical chimney swim-through — you enter it deep and come out shallow — is the thing everyone comes for.

What you’ll see. Clouds of fusiliers and trevally hunting through them; chevron barracuda and the odd great barracuda hanging alone; batfish; and the best whale shark odds anywhere near Koh Tao.

Where to position yourself. Do the chimney once, early, while the group is fresh. Then spend the rest of the dive on the side of the rock that faces the current, 10–18 m, and look out. Whale sharks at Sail Rock are usually spotted by the diver who was watching the blue, not the wall.

Our Sail Rock trip runs every Friday: two dives, an early start, and a longer boat ride than our local sites.

When to come

Months	What the pinnacles are like
March–May	The classic whale shark window; warm, calm seas, often the best visibility of the year.
June–August	Good conditions, fewer boats; big schools all season.
September–October	Second whale shark peak; occasional swell towards the end.
November–January	Monsoon months — wind and rain can keep boats from the pinnacles on bad days. We still dive when the sea allows.
February	Settling down; a good early-season month.

One caveat from our own logbooks: in 2026 we have been seeing whale sharks more often outside the traditional peaks. The months above are the historical pattern, not a promise either way.

Before you book

• All three are boat dives from Sairee Beach. The morning boat leaves around 6:45 and is the one that goes to the pinnacles; Sail Rock is a separate Friday trip.
• An Open Water certification is enough for Southwest and Sail Rock; for Chumphon, we recommend a few dives of experience first or doing it as part of the Advanced Explorer 30, which takes you to 30 m with an instructor.
• If you are a certified diver who has not dived for a while, a refresher in the bays the day before is money well spent — the pinnacles are not the place to remember how your BCD works.
• Fun dives for certified divers are 2,000 ฿ for two dives; the Friday Sail Rock trip is 2,800 ฿.

Frequently Asked Questions