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A reef manta ray seen head-on, its white belly and gill slits visible, passes above the sand in blue-green water, with small fish on the reef at right

Koh Tachai Pinnacle

ThailandAndaman Sea: Similan, Surin and LantaPelagicAdvanced

Koh Tachai Pinnacle is two granite pinnacles between 12 and 40 meters, south of the northernmost island of Similan National Park. It is the manta ray site of the Andaman Sea, with schools of barracudas and hundreds of trevallies circling too, and you dive it from Khao Lak.

Why dive Koh Tachai Pinnacle?

  • The manta ray site of the Andaman Sea, from December to May
  • Two granite pinnacles from 12 to 40 meters, covered in hard corals, soft corals and sea fans
  • Schools of barracudas in a vortex and hundreds of trevallies in the current
  • Whale sharks are not rare here
  • An island closed to tourists since 2016: no one on the beach, only boats at anchor offshore

The dive site on the map

Base: Khao Lak, 67 km as the crow flies.

See nearby dive sites on the map

Koh Tachai Pinnacle in pictures

Two reef manta rays pass above a coral block and a sandy bottom, one wing raised toward the surface, in milky water
The black-spotted white belly of a reef manta ray seen from below, with two remoras attached and its cephalic lobes unrolled, against a midnight blue background
The white sand beach of Koh Tachai lined with trees under a blue sky, with turquoise water on the right and a line of buoys offshore

What will you see at Koh Tachai Pinnacle?

Koh Tachai Pinnacle is first of all the manta ray site of the Andaman Sea. From December to May, they come to feed above the two pinnacles or circle around them, sometimes several at once. Whale sharks are not rare, passing through in the current that brings in all the open-water life: tight schools of barracudas spinning in a vortex above the top, hundreds of hunting trevallies, dogtooth tuna, and blacktip reef sharks at the edge of the boulders. A zebra shark rests on the sand between the rocks. The granite boulders are covered in hard corals, soft corals and big sea fans that shelter groupers, moray eels, butterflyfish and clouds of fusiliers; anemones and their clownfish fill the 13-meter plateau. The current makes the site rich: it brings the plankton that feeds the mantas and the small fish that feed everything else.

Sighting calendar
SpeciesJFMAMJJASONDNote
Reef manta raypeak seasonpeak seasonpeak seasonpeak seasonpeak seasonrarerarerarerarerarepossiblepeak seasonfrom December to May, feeding above the pinnacles or circling around them: the manta site of the Andaman Sea
Whale sharkpossiblepeak seasonpeak seasonpeak seasonpossiblerarerarerarerarerarepossiblepossiblenot rare, passing through in the current, mostly from February to April
Great barracudapeak seasonpeak seasonpeak seasonpeak seasonpeak seasonrarerarerarerarepeak seasonpeak seasonpeak seasontight schools spinning in a vortex above the top, large loners at the edge of the boulders
Zebra sharkpossiblepossiblepossiblepossiblepossiblerarerarerarerarepossiblepossiblepossibleresting on the sand between the boulders
Bigeye trevallypeak seasonpeak seasonpeak seasonpeak seasonpeak seasonrarerarerarerarepeak seasonpeak seasonpeak seasonby the hundreds above the reef, hunting in the current
Dogtooth tunapeak seasonpeak seasonpeak seasonpeak seasonpeak seasonrarerarerarerarepeak seasonpeak seasonpeak seasonby the hundreds above the reef, hunting in the current
Blacktip reef sharkpossiblepossiblepossiblepossiblepossiblerarerarerarerarepossiblepossiblepossiblepassing by at the edge of the boulders
Groupers, moray eels and fusilierspeak seasonpeak seasonpeak seasonpeak seasonpeak seasonrarerarerarerarepeak seasonpeak seasonpeak seasonin the cracks between the rocks and under the sea fans

peak seasonpossiblerare

What is diving like at Koh Tachai Pinnacle?

The site is two submerged pinnacles, the Twin Peaks, 500 meters south of the island: one huge granite boulder surrounded by big rocks, and two more pinnacles of boulders to the north. The tops are at 12 or 13 meters, the mooring lines are fixed to the bottom at 17 meters in the south and 27 meters in the east, and the sand drops to 35 or 40 meters outside the boulders. A typical dive stays between 18 and 24 meters, ending on the 13-meter plateau. Current is moderate to strong, often strong: you descend on the line, tuck in against the boulders for shelter, and ascend in open water under an inflatable buoy that marks the divers. Visibility ranges from 10 to 35 meters, as at Richelieu Rock. The level is intermediate to Advanced, and moderate air consumption helps, since the site is seen at depth. Divers without current experience should start with the Similans.

When to dive Koh Tachai Pinnacle?

idealgoodnot recommended

Mu Ko Similan National Park is open from October 15 to May 15; the 2026-2027 season opened on October 15, 2026. Manta rays and whale sharks show up mostly from December to May, and the heart of the season, from February to April, combines calm seas, water at 28 or 29 °C and big animals. The current does not follow the calendar: it depends on the tide and is strongest around the full moon and the new moon, when plankton rises and visibility drops below 10 meters on one side of the pinnacle. Day trips from Khao Lak run on Wednesdays, Fridays, Saturdays and Sundays; liveaboards pass almost every day. Off season, from mid-May to mid-October, the southwest monsoon closes the park.

How to get to Koh Tachai Pinnacle?

Koh Tachai is the northernmost island of Similan National Park, 72 kilometers from the port of Tap Lamu, which is itself 13 kilometers from Khao Lak. Liveaboards stop here between Koh Bon and Richelieu Rock: Manta Queen 2 (Khao Lak Scuba Adventures) does four days and three nights at Koh Bon, Koh Tachai and Richelieu Rock with ten dives for THB 20,000; Manta Queen 1 does five days and four nights from the Similans to Richelieu Rock, fifteen dives for THB 28,000; MV Andaman does four days and four nights on the northern route for THB 24,000 to 27,000, park fees included. On day trips, Khao Lak Explorer leaves Khao Lak at 8:30 a.m. by speedboat or catamaran, with 1 hour 20 minutes at sea, two dives at 10:15 a.m. and 1:15 p.m., and the return at 4:30 p.m., on Wednesdays, Fridays, Saturdays and Sundays from October 15 to May 15. It costs THB 5,300 by speedboat or THB 5,700 by catamaran, plus THB 700 for the park and THB 500 for gear, with hotel transfer, meals and one guide for four or five divers. Phuket airport is 60 kilometers south of Khao Lak.

Stay in Khao Lak

Where to stay near Koh Tachai Pinnacle?

Hotels, apartments and rooms around Khao Lak, with current prices.

Which hotels to choose near Koh Tachai Pinnacle?

Is Koh Tachai closed, and can you still dive the pinnacle?

Koh Tachai is Island 11 of Mu Ko Similan National Park, which it joined in 1998 along with Koh Bon. Its white sand beach drew so many boats that the Department of National Parks closed it to visitors on October 15, 2016, to let the environment recover; as of October 2026, no reopening date has been announced. The closure covers only the land and the beach: the dive sites around the island stay open, and boats anchor offshore. The pinnacle itself has never seen tourists: it lies 500 meters south of the island, below the surface.

How do you dive with the Koh Tachai manta rays?

Reef manta rays come here for the plankton that the current concentrates above the pinnacles and for the cleaning stations on the boulders. They arrive alone or several at once, circle wide above the top and come back several times in the same dive as long as nobody chases them. The rule is simple: stay low, against the rock, do not swim toward them, do not pass above them, do not touch. A manta you let come will approach within a meter; a manta you chase vanishes into the blue and does not come back. Each animal can be recognized by the spots on its belly, unique like a fingerprint.

What can you see on a Koh Tachai Pinnacle dive?

The first dive goes down the east mooring line, at 27 meters, then follows the big boulders of the main pinnacle between 18 and 24 meters, nose into the current, where the barracudas and trevallies circle and where mantas and whale sharks pass. A boulder formation at 21 meters serves as a landmark. The second dive starts from the south mooring line, at 17 meters, toward the two smaller northern pinnacles, covered in sea fans and soft corals, with groupers and moray eels in the cracks. Both dives end on the 13-meter plateau, among the anemones, before the ascent in the blue.

How do the Similan park quotas work for Koh Tachai?

Mu Ko Similan National Park, created in 1982, covers 140 square kilometers and eleven islands, 70 kilometers off the coast. Since it reopened in October 2018, it has capped visitors at 3,850 a day, including 525 divers and 3,325 swimmers and snorkelers. Tickets are bought on the Department of National Parks online booking system, and your identity must be confirmed before 8 a.m. on the day of departure. Dive centers handle it, but the diver quota fills up fast in high season, so book early. Sleeping on the islands has been banned since 2018: nights are spent on liveaboards or in Khao Lak.

Our tip

Descend fast and stay close to the boulders, as the current runs over the top. Do not swim toward the mantas: stay low and still, and they will circle within reach of your mask. Keep a third of your air for the ascent, away from the top, where the current speeds up.

Other dive sites nearby

Stay in Khao Lak

Image credits

Photos under free licenses, credited to their author; the link leads to the source.