Diving the Similan Islands in Thailand

The best of diving in Similan Islands, Surin and Richelieu Rock

Welcome to the exoticism, pure paradise, and incredible variety of marine life that have built the world-renowned reputation of diving in the Similan Islands, with over 500 species of hard and soft corals, and an even higher number of coral and pelagic fish.

Diving in the Similan Islands – Richelieu Rock – Koh Bon – Koh Tachai

The Similan – Koh Tachai – Koh Bon – Surin – Richelieu Rock diving liveaboards consist of two geologically distinct parts:

• The Similan Islands archipelago, the southernmost, consisting of 9 islands

• The Surin Islands archipelago further north, near the Burmese territorial waters

The Similan Islands Archipelago

The Similan Archipelago is a group of 9 uninhabited tropical islands located approximately 80 km northwest of Phuket. Declared a Marine National Park in 1982 to protect this ecosystem, three islands are completely off-limits to tourists to preserve an essential turtle nesting site in the Andaman Sea.

The topography of the islands and the underwater terrain is fantastic: huge eroded granite boulders, reminiscent of those in the Seychelles, witness the great continental drift millions of years ago, and they are covered in massive coral formations and giant gorgonians teeming with thousands of fish from the surface to depths of 40 meters and beyond.

Offering diverse landscapes, including canyons, arches, and caves, perfect for exploration and underwater photography enthusiasts, diving in the Similans also provides opportunities to encounter manta rays, leopard sharks, and blacktip or whitetip reef sharks during the high season.

Koh Bon and Koh Tachai

Diving in the Similan Islands of Thailand also includes Koh Bon and Koh Tachai.

Koh Bon, the first Similan island to the north, is of sedimentary origin.
It is a favorite place to encounter large manta rays during the migration period, which peaks between January and April.

A little further north is Koh Tachai, with its large reef plateau formed by a pile of granite boulders and giant gorgonians, with large schools of pelagic fish passing overhead.

Diving in the Similan Islands offers a variety of landscapes, including canyons, arches and caves.
Perfect for underwater exploration and photography, encounters with manta rays, leopard sharks and black and white tip sharks are frequent during the season.

The Surin Archipelago and Richelieu Rock Diving

Diving in the Similan Islands in Thailand is often associated with the Surin Islands. However, this is a very special archipelago made up of several islands, including the famous Richelieu Rock dive site. The Surin Islands offer a large number of dive sites, each as different as the next: coral gardens, clusters of granite rocks on which soft and hard corals have settled and which are home to a large number and variety of underwater species. The famous Richelieu Rock is a must for diving in the Thai archipelagos of the Similan and Surin islands. It is a rare and special ecosystem where the pyramid of species is still in perfect balance. Although the origin of the name recalls that of a Danish naval officer elevated to the rank of admiral in the Royal Thai Navy long ago, it was the first dives made by Captain Cousteau and his team aboard the Calypso in the 1980s on the rock – Hin Plo Naam in Thai – that gave it its name, because of the incomparable underwater richness of this rich Thai site and the color of the soft corals that carpet the rock everywhere, reminiscent of the red color of the robe of the former French Cardinal Richelieu. Each dive brings new discoveries, and for the fortunate ones a chance encounter with the majestic whale shark. Our diving cruises in the Similan Islands – Richelieu Rock – Koh Bon and Koh Tachai are the best way to discover this majestic place.

Best diving sites in Similan Islands

Boulder City is located southeast of the Similan Islands. This site offers a vast expanse of giant boulders resting on white sand in crystal-clear waters, ranging from 15 to 45 meters deep. Here, you’ll find giant orange gorgonians and fields of anemones, making it a favored spot for encountering leopard sharks and stingrays. It’s also not uncommon to spot manta rays during the season.

Also known as Hin Pae, Shark Fin Reef lies southeast of Island #3 (Koh Payan), featuring a massive granite ridge stretching nearly 1.5 kilometers, surrounded by white sandy areas. Smaller boulders can be found around the site, going down to a depth of 40 meters. There is a protected zone on this site that is always shielded from strong currents. Here, you’ll encounter leopard sharks, whitetip and blacktip reef sharks, as well as the distinctive humphead parrotfish schools, making this site truly unique.

Situated at the southeastern tip of Island #4 (Koh Miang), Bird Rock is scattered with boulders ranging from 10 to 40 meters deep. The rocks are covered in soft and yellow corals. The usual pelagic fauna includes trevallies, dogtooth tunas, and barracudas. The mild current allows for easy drift dives.

Known as Hide Away or Barracuda Point, this site is located northeast of Islands #5 and #6 (Koh Ha / Koh Hok). The terrain slopes down to a white sandy bottom. The rocks, ranging from 15 to 25 meters deep, are covered in both hard and soft corals, providing a rich coral reef ecosystem. The prevailing current generally follows the site’s direction.


Certainly one of the “deepest” sites in the Similan Islands. Starting with surface-level arches, the reef quickly drops on the west face, exceeding -50 meters. It is possible to spot gray reef sharks at the deep end. On the east side of the ridge, sheltered from the current, the rocks are covered in hard and soft corals, along with giant orange gorgonians. Turtles are frequent visitors, and large schools of silver jacks add to the allure.

This group of three giant granite blocks protrudes from the surface between Islands #7 and #8. Its shape resembles an elephant at low tide, earning it its nickname. The site is spectacular, featuring arches, canyons, crevices, and passages between the rocks, often leading to face-to-face encounters with beaked coral fish. Here, you’ll encounter turtles, gorgonians, schools of trevallies, and fusiliers on the gentler east face. This site is easy to explore even with some current.

Also known as “The Boulders,” this well-known site is situated northwest of Island #8. It consists of shallow granite blocks, reaching a maximum depth of 12 meters, providing an excellent setting for night dives. There’s a wide variety of soft and hard coral species, as well as lobsters, crabs, and shrimps in the crevices. The southern side is always protected from the current during the winter season and is relatively shallow, making it easy to return to the boat at the end of the dive.

Also referred to as Snapper Alley, this site lies east of Island #9 (Koh Bangu). The gently sloping white sandy bottom is dotted with coral blocks from the surface to 25 meters deep. The area boasts a wide variety of reef fish, and the current is generally weak, providing excellent visibility, particularly in the morning.

Located northeast of Island #9 (Koh Bangu), this site features an arch and three pyramid-shaped rocks at depths ranging from the surface to 30 meters. Whitetip reef sharks and stingrays are frequently spotted here, as well as turtles, tunas, mackerels, and barracudas.

Giant granite boulders form a network of canyons and crevices at North Point, with depths ranging from 10 to 30 meters. The site features large orange gorgonians, schools of platax, moray eels, barracudas, and turtles. The current at North Point is generally mild.

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Best dive sites Richelieu Rock and Surin Islands

Discover the wonders of Koh Bon, a must-visit dive site for enthusiasts of spectacular underwater landscapes. Located just a few kilometers from Phuket, this site offers a unique experience beneath the waves.


The pinnacle, covered in magnificent yellow soft corals, starts at a mere 18 meters deep and quickly plunges to over 50 meters. You’ll be amazed by the diversity of pelagic fish that inhabit the area, including barracudas, tunas, jacks, and sharks. But what truly sets Koh Bon apart is the almost regular opportunity to encounter majestic manta rays during the season. Get ready for incredible marine life encounters during your dive at Koh Bon.

Immerse yourself in the fascinating world of Koh Bon Point, a privileged spot for observing majestic manta rays during their migration season. Also known as West Ridge, this dive site extends from the surface to depths exceeding 35 meters.


This underwater cape acts as a natural magnet for pelagic species from deeper waters. You’ll be enchanted by the spectacle of yellow and pink soft corals contrasting with green hard corals, creating a stunning underwater landscape. Moreover, you’ll have the chance to consistently encounter schools of silver jacks, adding life and movement to this unforgettable diving experience at Koh Bon Point.

Explore the underwater marvels of Koh Tachai, a stunning dive site located off the island. You’ll be captivated by the two plateaus formed by piles of slabs and granite blocks, ranging from 10 to 35 meters deep. The rocks are covered in both hard and soft corals, creating a colorful and vibrant seascape.


During your dive, it’s common to come across whitetip and blacktip reef sharks, as well as nurse sharks. In the migration season, the plateau becomes a frequented passage for majestic manta rays and even the imposing whale sharks. Prepare for an unforgettable diving experience and exceptional encounters with marine life at Koh Tachai.

Explore the underwater treasures of Richelieu Rock, a renowned dive site located 45 minutes east of Surin. This famous rock, barely visible at low tide, is mainly submerged. Composed of sedimentary and limestone rocks, the reef is beautifully adorned with large anemones near the surface, while soft corals in shades of red, purple, and mauve cover its walls.


Thanks to its configuration, Richelieu Rock offers a sheltered area from currents at all times. Dives take place between 8 and 30 meters deep, offering an incredible diversity of attached fauna. It’s also a sanctuary for the rarest species, such as seahorses, ghost pipefish, leaf fish, frogfish, and nudibranchs. Additionally, due to its high plankton concentration under the influence of offshore currents, Richelieu Rock attracts the largest pelagic species.


Finally, Richelieu Rock is renowned as the best dive site for encounters with whale sharks. Prepare for spectacular dives where you can observe exceptional marine flora and fauna, as well as the unique opportunity to swim alongside these majestic whale sharks.

Discover the underwater splendors of Yellow Rock, an exceptional dive site located south of Koh Surin Tai. This site is renowned for its magnificent yellow soft corals covering the area between 10 and 25 meters deep. You’ll be dazzled by the richness of marine life that inhabits these waters.


Yellow Rock is home to a wide variety of reef fish, as well as pelagic species. The fauna is incredibly colorful, with yellowtail fusiliers and spotted eagle rays being common sights, along with frequent appearances of turtles and blue-spotted rays. Prepare for up-close encounters with these fascinating creatures during your dive at Yellow Rock.


It’s important to note that the current can be very strong at this location. However, this feature adds an exciting dimension to the diving experience, providing thrills for experienced divers.

Dive into the waters of Yellow Rock and discover a stunning underwater world, where yellow soft corals and colorful marine life will leave you with unforgettable memories.

Explore the underwater wonders of Koh Torinla, a small islet located south of Surin. This dive site offers depths ranging from 5 to 30 meters, where you’ll discover beautiful blocks and rocks covered in gorgonians and soft corals.


A deeper ridge allows for a dive along a coral mass parallel to the coast. You’ll be amazed by the diversity of hard corals that thrive in this area, providing a flourishing habitat for coral and pelagic fauna. During your dive, you may encounter tunas, jacks, barracudas, as well as spotted and marble rays.


Koh Torinla is a true paradise for marine life enthusiasts, offering a perfect combination of colorful corals and diverse marine fauna. Dive into the waters of Koh Torinla and prepare for an immersive diving experience, where you’ll be surrounded by a multitude of marine creatures evolving in their natural habitat.

Discover the underwater mysteries of Andaman Rock, a submerged rock at the southern tip of Koh Surin Tai. At depths ranging from 5 to 15 meters, you’ll be enchanted by the underwater scenery composed of hard corals that harbor a multitude of crustaceans, such as lobsters, crabs, and shrimps.


Andaman Rock is an ideal dive site for night diving enthusiasts. When the sun sets, this site transforms into a mysterious and fascinating world. Night dives at Andaman Rock offer unique opportunities to observe nocturnal marine life, witness corals come to life with vibrant colors, and encounter marine creatures that are more active during the night.


Dive into the dark waters of Andaman Rock and let yourself be captivated by unexpected encounters and astonishing underwater scenes that unfold during your night dives. This site offers a unique experience for divers who wish to explore the hidden wonders of nocturnal marine life.

Explore the underwater wonders of Koh Chi, a small island located north of Surin. Dives on the west coast of Koh Chi offer depths ranging from 5 to 25 meters, with an underwater terrain characterized by scattered rock blocks. You’ll be amazed by the graceful schools of fusiliers that roam these waters, as well as encounters with spotted eagle rays and whitetip and blacktip reef sharks.

The north coast of Koh Chi features a reef of hard corals where sea turtles are frequently observed. Dive into these crystal-clear waters and prepare to be enchanted by the graceful presence of these majestic creatures. Let yourself be captivated by the beauty of the corals and the diversity of marine life thriving in this preserved ecosystem.


Koh Chi is a true paradise for divers seeking diverse and marine-rich sites. Whether you are a beginner or experienced diver, the waters of Koh Chi have unforgettable encounters with the marine life of the Surin region in store for you.

Discover the underwater splendor of Hin Rap, a small island located north of the Surin Archipelago. This dive site presents an impressive decor of scattered granite blocks between 10 and 35 meters deep, adorned with formations of hard corals.


During your dive at Hin Rap, you may have the chance to encounter the majestic whitetip and blacktip reef sharks, adding excitement and emotion to your underwater experience. During the season, you may also have the opportunity to spot manta rays frequenting the area.

It’s important to note that the current can be strong at Hin Rap. However, this current also brings an abundance of marine life and contributes to the preservation of the underwater ecosystem of the region.


Dive into the waters of Hin Rap and prepare to be amazed by the hard coral formations, encounters with reef sharks, and possible sightings of manta rays. This unique diving experience will leave you with unforgettable memories and offer a fascinating perspective on the richness of marine life in the Surin Archipelago.

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