Thailand Dive & SailThailand Dive & Sail

By signing up, I agree to Thailand Dive & Sail Terms of Service, Privacy Policy, Guest Refund Policy, and Host Guarantee Terms

Already a member?

Thailand Dive & SailThailand Dive & Sail
Forgot password?

Don't have an account?

kohtachai

Similan ISlands

Dive Sites

KOH BON, KOH TACHAI & RICHELIEU ROCK DIVE-SITE GUIDE

Three absolutely fantastic dive-sites lie a short journey north and northeast of the Similans – Koh Bon, famous for frequent Manta Ray sightings and it’s awesome limestone wall and pinnacles; Koh Tachai, popular for its vast plateau, fringing granite rock formations and leopard sharks; and world-class Richelieu Rock, a huge, breathtaking horseshoe-formation just breaking the surface of the water, home to abundant rare marine life and stunning, soft purple coral gardens and sea fans. These dive sites are reached most conveniently on a liveaboard, please refer to Similan Liveaboard show to best reach them and the Similan Islands in one go.

Mu Koh Similan National Park was extended in 1998 to include the two northerly islands of Koh Tachai and Koh Bon, while Richelieu is such an unforgettable and nearby dive-site that all three of these attractions are usually included in most every live-aboard trip to the Similans. Day-trips to both Koh Bon and Richelieu Rock are also available. No dive-safari to the Similans is complete without a visit these sites.

Koh Tachai pinnacle is located a few hundred metres off the southern tip of Tachai Island. This famous Similan dive site is totally submerged, the shallowest depth around 12m. Two mooring buoys mark the exact location, one mooring goes down to around 15m, the other somewhat deeper at 33m.

A dive at Koh Tachai Pinnacle can often be the highlight of any Similan liveaboard trip. Dramatic topography, strong currents and a vast variety and quantity of fish and corals make this dive site truly memorable.

ABOUT KOH TACHAI PINNACLE

One huge dome-like granite boulder is the central feature of the dive site. Further large boulders are strewn all around this central rock creating canyons and coral plateaus rich in life. There are several flat areas at varying depths, stepping down to 30m and deeper.

Strong currents bring a constant flow of nutrients over the site and there is an abundance of large, impressive sea fans. Certain areas are carpeted in soft corals and sea whips, while dotted with hard coral bommies. All this is home to many species of fish.

tachai-fan-and-glass-fish

Similan ISlands

Dive Sites
tachai-manta-ray-image

Similan ISlands

Dive Sites

Large snappers, groupers and sweetlips lurk in the shadows under the boulders. Huge schools of bigeye snapper swim just off the bottom, while bigger schools of many types of fusiliers feed in the open water. The hard coral areas are home to many types of moray eels, anemones and anemone fish and an assortment of colourful butterfly fish and angelfish.

All around the dive site there is something to see. But it is the larger species of pelagic fish that is the big appeal at Koh Tachai Pinnacle, especially when the currents are strong.

“Huge quantities of chevron barracuda school during the day. The fusiliers are constantly harassed by the many types of trevally; giant and golden trevally being the most impressive.”

Heading into the second half of the Similan diving season, mid January to mid March, giant manta ray sightings are frequent with sometimes up to four or five individuals playing with the divers in the strong flow of water. They glide over the top of the pinnacle swooping around the different dive groups. Koh Tachai Pinnacle is also one of the best sites to encounter whale sharks. Sightings here are definitely on the increase rivalling that of nearby Richelieu Rock in the Surin Islands National Park.

Koh Tachai Pinnacle is also the firm favourite of most dive professionals working in the Similan Islands area. Richelieu Rock has the reputation as Thailand’s number one dive site, often the favourite dive on a Similan liveaboard. It is extremely rare to have a bad dive at Richelieu. But it is the unpredictability of Koh Tachai that keeps the dive site so exciting for dive masters and instructors who do hundreds of dives through the season. When the conditions are right, no dive site beats Koh Tachai.

There are only a few weekly scheduled day trips to Koh Tachai. All four and five day Similan liveaboard trips will have at least one dive at Koh Tachai Pinnacle, more if you are lucky.

Koh Tachai Pinnacle is definitely an advanced dive site, especially around full and dark moon. If you don’t enjoy diving in currents this site is probably not for you. However, if dived right, it can be an amazing dive. Please see the dive site briefing below.

kohtachaipinnaclemap

Similan ISlands

Dive Sites
Koh Tachai Pinnacle Dive Site Information
Site Name: Koh Tachai Pinnacle
GPS/Location: 40 km south of Koh Surin Tai, due south of Koh Tachai Island
Skill Level: Intermediate to advanced
Depth: 12 – 30+ m
Currents: Frequent, moderate to strong
Topography: Submerged plateau-shaped granite boulder centerpiece, surrounded by three separate reefs, each with different structures and marine life. Numerous canyons and overhangs with large sea fans
Highlights: Large plateau at 12 meters with huge sea fans. Check out the canyons and crevices
Marine Life: Whale Sharks, Manta Rays, Leopard sharks, Schooling Chevron Barracuda, Cube Boxfish, Giant Batfish, Trumpetfish, Giant Pufferfish, Oceanic Triggerfish
How to dive this site: Descend mooring line in a southerly direction to deepest side of site to maximum depth of 25-30 m, spiral up around the site following the contours of the rocks, direction depends upon current. We recommend that safety stops are also made on the mooring line in currents.
Our tips: Excellent multi-level dive site!
Please make sure to seek the mooring line as soon as you drop in, as currents are frequently moderate to very strong. After descent, protection may be found behind the rocks, depending on the direction of the current.
Keep your eyes on the sandy patches surrounding the pinnacle for Leopard sharks.
Suitable for both wide-angle and macro photography.
Photo tip: Excellent wide-angle photography site.

KOH TACHAI PINNACLE DIVE SITE BRIEFING

The best entry point for Koh Tachai Pinnacle is the shallower of the two mooring lines, usually the mooring buoy more to the west of the dive site.

Get Your Entry Right

If there is a strong current, a good captain will drop you up current from the morning buoy. Before jumping get a visual fix of the buoy location. After entering the water keep your focus on the buoy and make sure you grab the mooring line. Watch that the current doesn’t sweep you past. If you overshoot the line chances are you won’t be able to swim against the current back to the line. In short, if you miss the line you might end up missing the dive.

Descending down the line in current can be hard work. Keep going, it will get easier down on the site where boulders can provide some shelter. Hopefully inexperienced guides won’t hamper your descent by using the line for their ascent. Ascending on this mooring line is not a good idea. Be careful that your alternate air source does not free flow in the current.

Once down on the site you can shelter behind the large boulders to catch your breath. In strong currents it is still possible to navigate most areas of the dive site. You just have to look around and plan each part of the dive carefully. Look for the next point to shelter. Do not swim directly into the current. Stick close to the bottom, do not swim in the open water. Try zig zagging across the current, rather like tacking against the wind in a sailing boat. In the current is usually where you find the most action so it can be worth it even if a little exhausting.

tachai-and-diver

Similan ISlands

Dive Sites
tachai-bigeye-snapper

Similan ISlands

Dive Sites

If the current allows, a nice route is to head south west from the mooring line passing a couple of large high boulders on your right. In between the boulders are plenty of soft corals and nice fish life. The second boulder has a small canyon ending in a tight swim through. It’s a little too small to actually swim through without damaging the sea fans that grow here, but it is well worth a look. Rounding this rock will bring you to the West side of the dive site. You may have to kick hard to get around but it’s well worth it.

There is a large flat expanse on the west of the dive site at around 22-24m depth. This is one of the most beautiful parts of the site. A large hard coral bommie with a couple of giant gorgonian sea fans dominate this area. Next to the large boulder, snapper and slate sweetlips lurk in the shadows. There is usually a lot of bigeye snapper and retail butterfly fish schooling around the hard coral bommie. Watch out for Octopus in this area too. There is also a large anemone inhabited by some big Clark’s anemone fish.

Heading slightly deeper, still at the West but slowly turning north, two huge boulders plunge down into the depths. It’s usually around here you can see schooling chevron barracuda and trevally hunting. Between the two boulders is one of the liveliest areas on the site. Thousands upon thousands of glass fish seek shelter around the soft corals. Groupers and silversides dart through the schools creating a lot of movement in the water.

By now you will be heading round to the northern part of Koh Tachai Pinnacle. The two huge boulders are a good reference point to shallow up to around 18m depth. Alone, on a large boulder sits one of the finest, healthiest sea fans in the entire Similan Islands National Park. Well worth a short stop to admire.

There’s a very large hard coral garden on this northern section of the dive site. Dive slowly as there is a lot to see in this area. From this point in the dive you have three choices depending on remaining air and dive time.

The Second Half of the Dive

If the current is favourable and you have plenty of air and no-deco time remaining you can head further north to the less visited second pinnacle. If this is not an option you can continue circling the site round to the East. There isn’t as much coral life or sea fans here, but there are some very impressive boulders.

tachai-coral-scene

Similan ISlands

Dive Sites

If air supply is running low it is nice to shallow up onto the top of the dive site. From the northern part, head south up above the large dome like rock that is the centre of the dive site. Look out for great barracuda in this area. There will also be plenty of reefs and moray eels on top of the dome plus lots of anemone containing skunk anemone fish. If you are really lucky, giant manta rays like to sit in the current on top of the dive site.

Ascend Like a Professional

When it is time to end the dive, standard descent recommendations and using the mooring line for ascents are generally not a good idea. In fact, unless your dive boat is attached to the line,ascending on the line is unnecessary and can be stressful and dangerous.

In strong currents you will already know from descent that hanging on to the line is exhausting work. There is also little space at the 5m mark for many divers. Using the line as a group, divers bang each other, being hit by a tank can be a painful experience, there are bubbles everywhere and it is generally unpleasant. Also, you are exposed to jellyfish and other stinging organisms that drift at you in the current.

Remember your descent, ascending on the line will hamper other divers using the line to get down onto the dive site. And finally, once you surface on the line, no captain will be able to pick you up there, you will have to drift off the site to an area free of ropes and lines and other boats.

Experienced, professional divers will always drift off the dive site to ascend. Even in the strongest currents, once you drift away from the boulders the current slackens significantly. You can enjoy a tree free safety stop and surface where it is easy to be picked up by your boat.

KOH BON RIDGE Koh Bon

Koh Bon Ridge Map

Site Name: Koh Bon Ridge
Other Names: Manta Point, West Ridge
GPS / Location: Directly west of the ridge ascending off northwestern side Koh Bon island
Skill Level: Beginning to advanced
Depth: 5 – 30+
Currents: Occasion, mild to strong
Topographie: A sloping island ridge that continues on down into the water to a maximum depth of 30+ meters. Steep wall dive on the southern side of the ridge, rocky outcrops and canyons on the ridge itself, expansive coral gardens and smaller bommies on the northwestern side of the dive-site
Highlights: This is the only limestone island in Mu Koh Similan National Park, thus the water composition may sometimes be dense with particles and plankton, drawing numerous Manta Rays to the site regularly. Huge sponges and sea fans at depths 30+ meters
Marine Life: Manta Rays, Leopard sharks, Sea snakes, Octopus, Cuttle fish, Cleaner Wrasse, Shrimp, Lobster, Maldivian Sponge Snails, Abundant sea anemones, Giant Moray Eels, Andaman Sweetlips, Masked Bannerfish
How to dive this site: Drop in and ascend in protected bay area south of the tapering ridge, down to maximum depth heading in a due westerly direction. Zig-zag back up the ridge in an easterly direction. Depending on current, either continue on around the ridge to the east into the coral gardens, or return along the wall back to drop in point
Our tips: The wall itself is best viewed in the afternoon, as the sun shines brilliantly on the anemones and soft coral gardens
Photo tip: Excellent wide-angle photography site.

KOH BON PINNACLE Koh Bon

Koh Bon Pinnacle Map

Site Name: Koh Bon Pinnacle
Other Names:
GPS / Location: 200 m off the northwestern ridge of Koh Bon Island
Skill Level: Intermediate to advanced
Depth: 18 – 30+
Currents: Moderate to strong
Topographie: Two huge limestone pinnacles lying north to south, sandy bottom, few soft corals
Highlights: This is a short, deep, intense and entertaining dive. A dive-site swarming with fish, like being inside an aquarium
Look out for Leopard sharks in between the two main rocks
Marine Life: Leopard sharks, Manta Rays (January through April), Schooling trevallies, Oriental and Andaman Sweetlips, Giant Moray Eels, Emperor Angelfish, Trumpetfish, Cuttlefish
How to dive this site: Drop in and ascend on S and ascend to to maximum depth at the sandy bottom of the S rock, spiraling up around and through both rocks to end dive with safety stop at approximately drop-in location
Our tips: This site will be located by credible dive operators with the assistance of a depth sounder. The use of a drop line to locate the rocks is not recommended, as it destroys the corals!
Photo tip: Excellent wide-angle photography site.

KOH TACTAHI PINNACLE DIVE SITE MAP

Koh Tachai Pinnacle Map

KOH TACHAI PINNACLE DIVE SITE INFORMATION
SITE NAME: Koh Tachai Pinnacle
GPS/LOCATION: 40 km south of Koh Surin Tai, due south of Koh Tachai Island
SKILL LEVEL: Intermediate to advanced
DEPTH: 12 – 30+ m
CURRENTS: Frequent, moderate to strong
TOPOGRAPHY: Submerged plateau-shaped granite boulder centerpiece, surrounded by three separate reefs, each with different structures and marine life. Numerous canyons and overhangs with large sea fans
HIGHLIGHTS: Large plateau at 12 meters with huge sea fans. Check out the canyons and crevices
MARINE LIFE: Whale Sharks, Manta Rays, Leopard sharks, Schooling Chevron Barracuda, Cube Boxfish, Giant Batfish, Trumpetfish, Giant Pufferfish, Oceanic Triggerfish
HOW TO DIVE THIS SITE: Descend mooring line in a southerly direction to deepest side of site to maximum depth of 25-30 m, spiral up around the site following the contours of the rocks, direction depends upon current. We recommend that safety stops are also made on the mooring line in currents.
OUR TIPS: Excellent multi-level dive site!
Please make sure to seek the mooring line as soon as you drop in, as currents are frequently moderate to very strong. After descent, protection may be found behind the rocks, depending on the direction of the current.
Keep your eyes on the sandy patches surrounding the pinnacle for Leopard sharks.
Suitable for both wide-angle and macro photography.
PHOTO TIP: Excellent wide-angle photography site.

ABOUT KOH TACHAI PINNACLE

One huge dome-like granite boulder is the central feature of the dive site. Further large boulders are strewn all around this central rock creating canyons and coral plateaus rich in life. There are several flat areas at varying depths, stepping down to 30m and deeper.

Strong currents bring a constant flow of nutrients over the site and there is an abundance of large, impressive sea fans. Certain areas are carpeted in soft corals and sea whips, while dotted with hard coral bommies. All this is home to many species of fish.

Large snappers, groupers and sweetlips lurk in the shadows under the boulders. Huge schools of bigeye snapper swim just off the bottom, while bigger schools of many types of fusiliers feed in the open water. The hard coral areas are home to many types of moray eels, anemones and anemone fish and an assortment of colourful butterfly fish and angelfish.

All around the dive site there is something to see. But it is the larger species of pelagic fish that is the big appeal at Koh Tachai Pinnacle, especially when the currents are strong.

“Huge quantities of chevron barracuda school during the day. The fusiliers are constantly harassed by the many types of trevally; giant and golden trevally being the most impressive.”

Heading into the second half of the Similan diving season, mid January to mid March, giant manta ray sightings are frequent with sometimes up to four or five individuals playing with the divers in the strong flow of water. They glide over the top of the pinnacle swooping around the different dive groups. Koh Tachai Pinnacle is also one of the best sites to encounter whale sharks. Sightings here are definitely on the increase rivalling that of nearby Richelieu Rock in the Surin Islands National Park.

Koh Tachai Pinnacle is also the firm favourite of most dive professionals working in the Similan Islands area. Richelieu Rock has the reputation as Thailand’s number one dive site, often the favourite dive on a Similan liveaboard. It is extremely rare to have a bad dive at Richelieu. But it is the unpredictability of Koh Tachai that keeps the dive site so exciting for dive masters and instructors who do hundreds of dives through the season. When the conditions are right, no dive site beats Koh Tachai.

There are only a few weekly scheduled day trips to Koh Tachai. All four and five day Similan liveaboard trips will have at least one dive at Koh Tachai Pinnacle, more if you are lucky.

Koh Tachai Pinnacle is definitely an advanced dive site, especially around full and dark moon. If you don’t enjoy diving in currents this site is probably not for you. However, if dived right, it can be an amazing dive. Please see the dive site briefing below.

RICHELIEU ROCK Surin Islands National Park

Richelieu Rock Map

Site Name: Richelieu Rock
Other Names:
GPS / Location: 14 km east of Koh Surin Nua
Skill Level: Intermediate to advanced
Depth: 0 – 30+
Currents: Moderate to strong
Topographie: Wall dive. Granite, horseshoe-shaped rocky outcrop surrounded by smaller submerged pinnacles. The main pinnacle breaks the surface at low tide
Highlights: Huge marine diversity! Excellent for large pelagics. Bright purple soft corals dot the site, hence the connection to the purple robes of Cardinal Richelieu. Considered the best dive-site in Thailand
Marine Life: Whale sharks, Manta Rays, Chevron Barracuda , Tuna , Trevallies, Harlequin Shrimp, Pineapple Fish, Seahorses, Schooling Bannerfish, Moray Eels, Cube Boxfish and, and, and… the possibilities are immense!
How to dive this site: Descend on mooring line or in direct vicinity of pinnacle, proceed to maximum depth and shallow up as currents allow. Protection on inside or outside of horseshoe formation depending on direction of current
Our tips: Examine the sea fans closely for seahorses.
Bring a torch to explore the smaller recesses in the walls to discover rare pineapple fish and harlequin shrimp
Photo tip: A wide-angle and macro photography dream