Best Dive Sites in Similan Islands

The Similan Islands National Park is a series of strikingly beautiful granite and jungle islands in Thailand with some stunning beaches and great undersea diversity.

Diving here normally originates from Phuket and is done by live aboards running anywhere from two-day to two week trips. The water clarity and healthy reefs make these islands the focal point of regional diving.

Varied and full of color, the southern islands are numbered one through nine and host a number of live aboards that launch from the western Thai coast. These numerous islands are balanced by the large northern islands of Ko Bon, a beautiful piece of limestone, and Ko Tachai, which has attractive sand beaches and some good offshore dives.

Since the tsunami, the eastern coasts have been the favored aspect of these islands to dive. The terrain features stunning hard corals, soft corals, sea fans and immense coral heads, and they range from shallow to quite deep, and from no currents to pretty brisk ones.

An extremely photogenic place, this is where many of the signature Thailand diving images are made, especially those with wide angle vistas and big gorgonian sea fans.

Fish are also well-represented, with anything from mantas and leopard sharks to ornate ghost pipefish, blue spotted jawfish, Andaman sweet lips and nudibranchs to be found.

1. Coral Gardens

Location: North side of Similan (Ko Huang)
Depth: 1-80ft (0-24m)
Access: Live aboard
Expertise Rating: Novice

Both snorkelers and divers will like this spot, as the reef runs along the island’s beach area and produces opportunities for rewarding snorkeling or a nice, long dive whilst checking out the variety of marine life on show.

Just about every dive destination seems to have a ‘Coral Gardens’ dive site, and this is the Similans’ entry. A great variety of acropora corals, such as staghorns and table corals, mix with other plating and hard corals to form large life-filled patches and colorful scapes from deep to very shallow. The deeper sandy areas hold bluespotted stingrays that throw up clouds of sand as they dig for crustaceans.

Swaying in the currents are garden eels, which disappear if you breathe too quickly or move too closely. They feed on current-driven morsels mostly too small for the eye to see. Move up to see more hard corals and fish life, like angels, parrotfish and lots of butterflyfish.

2. Boulder City

Location: 1.6 nautical miles (3km) southeast of Similan (Ko Payan)
Depth: 40-130ft (12-40m)
Access: Live aboard
Expertise Rating: Intermediate

Yellowback fusiliers thrive at Boulder CityThis is a deeper site with a couple of moorings leading down to a series of large boulders. Close to Shark Fin Reef, it’s a good area to poke around in the deep at first, to see if there are any leopard sharks or mantas down at the southern end, before checking for other fish life among the boulders while working back up to shallower waters.

The bottom can be as deep as 130ft in the south, with sandy areas 70ft to80ft and boulders rising to within 40ft to 60ft of the surface. Coral growth here is pretty, with sea fans and lots of glassy fish attracting lionfish and scorpionfish. Look also for various groupers, including big marbled groupers, coral groupers and peacock groupers.

Finish up by heading back toward the center of the site, where the shallowest rock provides some fish watching before heading to the deco stop.

3. Shark Fin Reef (Hin Pae)

Location: 0.87 nautical miles (1.6km) southeast of Similan (Ko Payan)
Depth: 0-95ft (0-30m)
Access: Live aboard
Expertise Rating: Intermediate

Southeast of Ko Payan, this is a well-visited site that has pretty coral gardens in the northwest and boulders, fish and swim-throughs farther south. The mooring is near the mid-point of these two features and divers can proceed either way. For those who want to see fusiliers, you’ve come to the right place.

Seemingly endless schools of various types, including yellowback, neon and yellowtails, all roam the boulders in huge schools. These boulders also offer passages that are enjoyable to dive around and through. Look for stands of evergreen tubastrea corals with lots of small damsels, growing atop the boulders. Where the rocks pierce the surface in three places, they are said to resemble shark fins, giving the reef its name.

Schools of five-line snapper also enjoy this environment. There can be some current here, which the big rocks deflect. The reef is more open to the north, with good coral gardens and fish diversity. At about 90ft whitetip and leopard sharks can sometimes be seen in the deeper sandy areas. The site also has some big coral heads and large boulders in the channels.

4. East of Eden

Location: East side of Similan (Ko Payu)
Depth: 10-118ft (3-36m)
Access: Live aboard
Expertise Rating: Intermediate

Considered one of the must-do dives in the area, thanks to a beautiful coral bommie that rises from the deep, along with clear water and prolific coral growth, this site has two moorings toward the end of Ko Payu, on the east side.

There is lots of hard coral here on a graduated slope. Many coral heads and small rocks are attractively decorated with an artist’s palette of soft coral colors and large sea fans. Manta rays have also been seen here on occasion, so it doesn’t hurt to glance out into the blue every once in a while. Sport divers may want to start at the mooring closest to the point for a longer, more leisurely dive along the coral gardens, while photographers should head down to the bigger bommies to get some of the very pretty reef shots this site has to offer.

Look for shoals of glassfish and other small fish covering well-landscaped coral heads. Spotted groupers and lionfish are in heaven here with all the readily-available food, while deeper down look for fire gobies and blue-spotted stingrays in the sand. Coral cover runs up into the shallows, making this an interesting multi-level dive. Table corals with small damsels, sheets of plate corals with nudibranchs underneath and both star and brain corals all dot the reef.

Up top a long deco stop in a beautiful coral garden is available. Some rubble patches may be the result of decades- old dynamite damage, but these are slowly being overtaken by broad branching coral patches that hold refuge for many reef fish, including leaf fish and juvenile emperors. The site has a good collection of anthias and basslets, including jewel fairy basslets.

Look as well for the toothy moustache triggerfish that nest in some areas, groups of red-tailed butterflyfish roaming over the staghorn beds and schools of bigeye snappers. This makes for a good third of fourth dive that can be done at a leisurely pace, to observe and absorb everything to be found.

5. West of Sweden

Location: North Tip of Similan (Ko Payu)
Depth: 0-130ft (5-40m)
Access: Live aboard
Expertise Rating: Intermediate

The name of this site is a good example of Thai humor. Located west of the East of Eden site, local dive guides discovered this site around 2004 and started diving it frequently after the tsunami in December of that year trashed several of the popular area reefs.

There are some small- to medium sized granite boulders, as well as a welllit swim-through near the reeftop that starts at 15ft and exits at about 40ft. There can be some currents and upwellings at this site that make the water a bit chilly at times. (This is generally true of dives at islands 7 and 8 in the Similans.)

Divers have the opportunity to go quite deep here, as rocky ridges run west and drop from 35ft down past 140ft. Some beautiful orange gorgonian sea fans can be seen here, as well as bommies with sea whips, fans and soft corals.

From about 40ft to 70ft there are some good patches of hard corals. Deeper down the ridge in the sand, look for whip corals, along with beautiful little harp or candelabra corals in shades of deep red. Small boulders and bog coral heads have some very pretty soft pink, purple and white corals. Keep a look out also down deep in the south end at the sand alley for whitetip reef sharks.

Currents may bring in giant and bluefin trevally, as well as an occasional visit by a manta or sea turtle. Schooling butterflyfish, red tooth triggerfish and lined surgeonfish can all be seen here, as can neon and yellowback fusiliers. Smaller sea life found here includes frogfish and ghost pipefish. Ribbon eels are also seen poking from the sea floor and crevices.

6. Elephant’s Head (Hin Pusar)

Location: Between Similan (KoPayu) & Similan (Ko Similan)
Depth: 16-118ft (5-36m)
Access: Live aboard
Expertise Rating: Intermediate

This is the area’s ultimate novelty dive, with huge boulders stacked across the ocean floor and protruding from the sea. These form an amazing maze of huge proportions which holds a lot of marine life and is a blast to swim over, under, around and through.

Fish life includes whitetip sharks and occasional leopard sharks on the deeper outer reef areas, which are mostly sand and rubble. But it’s in around the rocks that the fish variety here becomes apparent. Whitetips also like to hide under cracks and deep overhangs here, and guides usually know where they hang out. These crevices are also hiding places for the solitary great barracuda.

Some corals have attached to the boulders; look for small fans, soft corals and some big table corals that appear to be cleaning stations for blue-stripe wrasse. Pretty fish include powder-blue tangs and the odd unicornfish. Blue-lined angelfish and titan triggerfish also like to swim along the upper parts of the boulders, and a few sea anemones with pink anemonefish are also to be found at shallow depths.

One can follow the slope of the elephant’s head giant boulder from below all the way up to where it breaks the surface. The sides are kept clean by grazing surgeonfish and other herbivores. A fun dive with lots to see and lots of finning to cover the area, it really takes a couple of dives to see it all.

7. Beacon Point

Location: Southeast end of Similan (Ko Similan)
Depth: 16-118ft (5-36m)
Access: Live aboard
Expertise Rating: Intermediate

Ring angelfishAt the south end of the more sedate Beacon Beach, Beacon Point can be a deeper dive. Head down a long sloping drop-off to a sandy bottom at 115ft, where there are usually stingrays hidding in the sand or foraging for food.

One can then work back up the slope whilst checking the hard corals for invertebrate and fish life, including Moorish idols and the similar looking bannerfish. Trumpetfish and lined snapper are also found on the reef, and the current may also bring schools of smaller fish, such as damselfish and chromis.

Look also for the cleaning stations that often feature one or more fish hanging in parallel while cleaner wrasse pick over them. When finning along here, it is best to surface or head back to the shallows before going around the point of the island.

8. Beacon Beach

Location: East side of Similan (Ko Similan)
Depth: 20-100ft (6-30m)
Access: Live aboard
Expertise Rating: Novice

This site offers a broad variety of corals and good fish life, thanks to the artificial reef here which until 2002 was the charter boat Atlantis X. The boat’s captain had tried to beach it when it took on water, but it eventually sank and settled away from the beach in 50ft to 105ft of water.

Coral and encrusting sponges, some crinoids and other marine life are gradually forming on the ship. Batfish, who seem to like shipwrecks, along with some lionfish, have also found their way here and set up home. The ship’s ribs are still intact and it has had some algae growth on it however, it’s not as pretty as some shipwrecks.

The reef area is a hard coral slope with good lettuce corals, plating corals and bubble corals. Once hit by a crown-ofthorns starfish invasion, the area has bounced back well, showing how this natural occurrence can cull corals and leave space for new growth in a competitive reef.

Bigeye snappers, goatfish, nervous hawkfish and roaming trumpetfish are all part of the fish scene at this site, which every level of diver can enjoy.

9. Turtle Rock

Location: Northwest side of Similan (Ko Similan)
Depth: 30-100ft (9-30m)
Access: Live aboard
Expertise Rating: Intermediate

Located just off Ko Similan, some nice hard coral gardens here offer divers and snorkelers the opportunity for a good dive in a healthy coral environment. A turtle-shaped rock gives the site its name, as opposed to regular turtle sightings. However you will encounter lots of reef fish, including lined triggers, various parrotfish species and small schools of bannerfish.

There are some nice anemones with pink anemonefish here, along with bluering and emperor angels, parrotfish and some grazers, such as surgeonfish. The reef has lots of branching coral beds and chromis are thick in the water column above, retreating to the safety of the beaches whenever a diver fins past or a jack slashes through their mass.

Nearby Donald Duck Bay (or Campbell’s Bay) is often reserved for a night dive and can also be good for snorkelers. It’s a popular mooring site for all sizes of live aboard and sailboats, so be aware of the traffic.

10. Snapper Alley

Location: Southwest tip of Similan (Ko Bangu)
Depth: 20-118ft (6-36m)
Access: Live aboard
Expertise Rating: Intermediate

A formation of granite boulders makes a pleasant dive site, ranging from quite deep to more manageable depths. Evergreen tube corals (with attendant black damsels) like to grow on the boulders and reef bottom in the currents.

Black coral trees can also be found, while current- fed areas have good soft corals. Sheltered undercuts of coral heads and boulders also make good refuges for some rather large lobsters and crabs. Look in the same area for lazy puffers and resting whitetip sharks.

Lots of beautiful lined snappers form golden shoals over the upper reef here, giving the site its name. Enjoy them and the schooling yellowback fusiliers as you complete the shallower section at the end of this dive.

11. Bommies

Location: South side of Similan (Ko Bangu)
Depth: 59-80ft (18-25m)
Access: Live aboard
Expertise Rating: Intermediate

allied cowrieDrop down to a series of five large coral heads (or bommies) which rise up from a beautiful and reflective white sand floor, at this lovely little spot along southern Ko Bangu.

Like some of the other well-decorated Surin Island sites, this park dive also has a good array of sea fans and soft corals in red, orange and yellow hues. Look under the bommies for nudibranchs and small crabs, but be careful to watch your bubbles so they don’t rise up too close to the corals and scour them.

Night dives here produce gorgonian crabs, spindle cowries and feather stars in the sea fans, and also bring out the odd sponge crab and decorator crab.

12. Songraki Reef

Location: Northeast side of Similan (Ko Bangu)
Depth: 40-140ft (12-35m)
Access: Live aboard
Expertise Rating: Intermediate

One of Thailand’s newest sites, this holds some of the healthiest and best-looking hard coral cover of any reef in the Similans. Sometimes called Three Trees, it is located off the northeast tip of Ko Bangu and consists of a series of pinnacles and granite boulders that step down into the sea past 130ft.

Brain, mushroom, staghorn and table corals that start in 40ft and are scattered around the slope and sandy bottom are contrasted by soft corals and whitepolyped gorgonian sea fans. Loads of tiny baitfish hover over this seascape. This site also makes for a great multilevel dive.

Some of the mushroom corals are massive, starting in 70ft and rising up to top out at 40ft. Fish life includes schools of longfin batfish and chevron barracuda, and even an occasional manta. Whitetips and zebra sharks are frequently seen in the deep and on the bottom, and even reef blacktips have been seen roaming about.

More than six species of butterflyfish have been observed here, making the reef bright and colorful with their presence. In the shallower parts of the reef, look for milkfish schools and wandering spearing mantis shrimp. This is also a favorite haunt of hawksbill sea turtles. New and exciting, this reef will please virtually every level of diver.

13. The Pinnacle

Location: North of Similan (Ko Bangu)
Depth: 16-110ft (5-32m)
Access: Live aboard
Expertise Rating: Intermediate

This site is located north of Ko Bangu with a mooring leading to large rocks that extend down to 100ft, surrounded by a sand and hard coral environment.

Coming as close as 18ft to the surface, the rocks and reef are stepped down, and the site features a very healthy and active Acropora or staghorn coral patch full of small tropicals, butterfly and angelfish, anthias and chromis. There are orange sea fans to observe and the site has a good collection of scattered large barrel sponges.

There is even tubastrea coral growth in some areas of the reef. A small hawksbill turtle is seen here on most dives and the endemic (and sometimes solitary) Andaman sweetlips is also found on the reef. Lots of fusiliers keep the site lively, and mantas have been seen here as well.

14. Ko Bon

Location: 11 nautical miles (21km) north of the Similan Islands
Depth: 15-130ft (5-40m)
Access: Live aboard
Expertise Rating: Intermediate

Ko Bon has become very popular in recent years, as there are a couple of manta ray cleaning stations on the reef, along with an area where these creatures like to feed and play. There seems to be a lot of boat traffic at times, but most divers swim/fin a lot here.

It’s best to find a spot near the beautiful staghorn coral gardens on the west side, or just at the end of the sloping ridge at the south, then wait for big rays to swim in. Stay very low and breathe lightly, and you’ll be able to watch some very big (and somewhat shark-bitten) mantas cleaning, feeding and playing.

Most dives start near a blowhole just prior to the southwest point, where the water churns into a froth. With reef on the right, one can swim out to the point and follow the ridge down past 100ft, where a small promontory offers hard coral cleaning stations and lots of current-driven fish life. Crevalle jacks, a ribbon-like yellowtail snapper school, big marbled groupers, longfin pompano and dogtooth tuna all ply these waters, as well as mantas and even a whale shark on occasion.

Shallower areas on the west side and along the ridge have small soft corals and big table corals, bommies with lionfish and sweepers galore, orange-lined triggerfish and moray eels. On the southeast side there’s a sandy plain at 90 to 100ft where one can either hide from the current or catch it and drift to the ridge.

Look for Andaman sweetlips along the rocky cuts and plates here. Hanging at the west side, the staghorn bed is very rewarding. There’s a manta cleaning station and lots of chromis. Stay low and mantas will circle many times as they get cleaned by blue-stripe and bluehead wrasses. The place is really fun at dusk with jacks and groupers wreaking havoc on the staghorn bed.

Five species of trevally roam here individually or in packs, and moray eels and sea snakes can also be seen on the hunt. The site also has leopard sharks, lionfish, cuttlefish and even mating octopi. If there is no surge, try to come up close to the blowhole where boat traffic is low.

As many as a dozen boats and ships have been counted here at one time, so use your head when it comes to surfacing and keep plenty of air on hand so you can swim to a safe ascent point.

If you do get caught in an openwater drift here, use a safety sausage. Sitting far north, almost to the Thai and Burmese border, Ko Bon and Ko Tachai used to be considered a kind of no-man’s land, and have only recently been included in the Similans.

15. Ko Bon Pinnacle

Location: 11 nautical miles (21km) north of the Similan Islands
Depth: 60-130ft (18-40m)
Access: Live aboard
Expertise Rating: Advanced

This site isn’t for the faint hearted and it doesn’t hurt to be fit here either, as it can be tricky just reaching the top of the pinnacle when the currents are strong. You have to get down quickly and hope you’ve timed it well-enough to let the currents carry you to this deep site.

A reef hook certainly doesn’t hurt when diving here. What makes it all worthwhile is the big fish action. Divers have reported as many as seven mantas and a mobula all swimming around the pinnacle on one dive, and whale sharks are known to come here as well, on a less frequent basis.

16. Ko Tachai

Location: 12 nautical miles (23km) north of the Ko Bon
Depth: 40-118ft (12-36m)
Access: Live aboard
Expertise Rating: Intermediate

The best diving at this northern Similan island is in the south, where two moorings lead to a ridge starting at 40ft and falling off to around 120ft at the sandy bottom. Known as Twin Peaks, the formation has a pinnacle on the north end and a big, round bommielike structure at the south.

This attracts manta rays that come in to clean and do some feeding. One may have to hide to see some of the action, as this place can be rather currently, but when the mantas are at the cleaning area it can be beautiful, with low-lying coral gardens and lots of chromis and basslets giving life and color to the reef. Some of the nearby corals have good fans and soft corals growing on them as well. This is also a good place to see sponge life with big barrels filtering current-supplied nutrients.

There’s an especially eye-catching neon green sea anemone at the south end at around 60ft, with Clark’s anemonefish and nice whitecap shrimp. Ghost pipefish, frogfish and leopard blennies are sometimes seen here as well, and sleeping leopard sharks are also a possibility in deeper areas. Look too for some great schools of fusiliers, batfish and chevron barracuda, along with pelagics like rainbow runners and dogtooth tuna.

Pairs of red-tailed butterflyfish, small schools of grunts and silver sweetlips all like to face into the current here. Visibility can be quite good, but occasionally a thermoclime of colder and lower visibility water will rush in, reducing visibility considerably. But it does seem to increase fish activity when this happens and particularly right before it happens.

This is a very active spot and can be enjoyed over multiple dives. Deco stops are often done at the mooring lines, or sometimes by drifting with the current for an open-water decompression – if that’s the case, be sure to use a safety sausage.

The Similan Islands really are one of the top rated dive sites in the world. Go explore and see this beautiful destination for yourself.