Sail rock: Amazing site for huge school of fish and whale shark in the gulf of Thailand



Sail rock is the representative diving site in the gulf of Thailand, which locates on the east side of Malay peninsula. If you say that the champion diving site in Andaman sea, on the west side of Malay peninsula is Richelieu rock, the champion on the east side is definitely Sail rock.


Where is Sail rock?

There are three islands in the south of the gulf of Thailand and the three islands are lined up from south to north. The southernmost island is Koh Samui, a popular resort island, the midde is Koh Pangan, a island of full moon party and the northernmost is Koh Tao, an island of divers and backpackers. The rock is located at the middle between Koh Tao and Koh Pangan.

Unique features of the gulf of Thailand

The gulf of Thailand is a quite unique sea, comparing the other Southeast Asian seas. What is unique is a relatively closed environment into which no large ocean current flows, due to two large peninsulas surrounding the gulf and its shallow bottom, that makes its tide ebbs and flows only once a day. And due to this closed environment, there is an ecosystem in which the same species prominently prospers. As for a number of kind of species, there are probably less kinds than in the other seas, but instead, each school of fish become much larger. The sail rock stands on the bottom of 30 meters depth and sticks its top out of the surface. Tons of fish is gathered around the rock because there is not any other reef around it. Those factors make the scene absolutely impressive.

It stands on the bottom of 30 meters depth and sticks its top out of the surface. Tons of fish is gathered around the rock because there is not any other reef around the Sail rock.

Highlights of the Sail rock

Huge school of big eye trevally

First of all, one of the greatest things at the Sail rock is big school of big eye trevally. You can meet them almost every time when you are at the site, although they occasionally go down into deep and turbid water. They often swim in so crowded group that you cannot see around. They are quite impressive.

Bat fish

School of Bat fish is also astonishing. The School sometimes grows a group of up to 100 or 300 bat fish. You hardly meet a school that fills a whole view you can see in other seas, you relatively often see a group of about 20 bat fish, though. You sometimes need a little luck to see them because the scale of the school depends on season and occasionally big group swim at a distance from the rock.

Chevron barracuda and Pickhandle barracuda

You can see some barracudas aroud the Sail rock. Chevron barracuda are gathered in a big crowded school. Chevron barracuda is middle size in barracudas and it is 50-80 cm in the length.

Aother barracuda is pick handle barracuda. They are big barracuda more than 1 meter in the length and have yellow tail fins. They tends not to be crowded and don’t make so big group, but each individual is big and impressive.

Anyway, you can see huge schools of fish

In addition to fish mentioned above, Oxeye scad, Bigeye snapper, fusiliers and so on make a big crowded schools around the rock. That is a really exciting scene.

Whale shark

What makes the site special other than this astonishing big crowd of fish is whale shark. You can see whale shark in natural environment at relatively high probability, although it is not so certain as in Maldives or Galapagos. You can see them in Andaman sea that faces the other side of Malay peninsula, but I think you have more chances in the Sail rock and other sea around Koh Tao. One more special feature about whale shark around the Sail rock is that they appears in the middle of huge school of fish. Whale shark and a school of big eye trevally, whale shark and a school of bat fish, those are absolutely exciting scenes.

Unfortunately, I don’t have a photo of whale shark at the Sail rock, so I will post a photo of whale shark taken at Chumporn pinnacle that locates in the same area as the Sailrock instead.

And here is a link to a diving service that have great photos of whale shark at the rock.

SCUBA Diving Koh Tao | Big Blue | Thailands Best Dive School
Go diving in Koh Tao with the worlds number 1 SSI dive school. First class SCUBA instructors, 3 dedicated boats and our ...


There is a vertical cave in the rock. It is called The chimney. The entrances are at 20 meters deep, 15 meters, and 8 meters. You can see a beautiful shine when you look up from the bottom of the cave.

Travel infromation

How to get there?

You can use a diving service from Koh Tao, Koh Pangan or Koh Samui to dive at the Sail rock. It takes about one hour by speed boat from Koh Samui. They usually leave Koh Samui by speed boat in the morning, then have two dives at the rock, after that they return to the island. From Koh Tao, you can get on a large diving boat and it brings you to the rock in one and half or two hours. Usually you can have two dives at the rock and another dive at Southwest pinnacle or a site around Koh Tao in a day, then return to the island.

The most convenient way to Koh Samui is by air. There are many flights between Bangkok and Koh Samui. As of January 2019, you can have other direct flights to Koh Samui from Hong Kong, Guangzhou, Kunming, Chengdu, Singapore, Kuala Lumpur, Phuket, and Krabi. There are also ways that you go to Chumporn or Surat Thani by bus or train and get on a boat from there to Koh Samui, but these take so much longer than by plane that I recommend you to take plane unless you have special purpose to use these transportation.

Two hours trip by boat brings you to Koh Tao from Koh Samui after you reach Koh Samui by plane. There are two main operation companies. Seatran Discovery and Lomprayah. Personally, I prefer Seatran discovery because its port is nearer from the airport, and its boat is usually not so crowded as Lomprayah. You can also choose to get to Chumporn by bus or train and get on a boat from there to reach Koh Tao. But it takes quite much time.


The best season for diving there is from March to October. The rainy season is from late November to January. This rainy season differs from the other area of Thailand. Species of fish you can see don’t so depend on season, but it is said that the probability for whale shark rise from March to May and from August and October.