Dive site information & map of Boulder city at the Similan islands

Boulder city dive site information

Boulder City dive site

About Similan islands dive site Boulder City

Boulder City- Only 1 kilometre southeast of Similan Island 3 (Koh Pa-Yan), and about 400 meters of Shark Fin Reef, hundreds of huge granite boulders and rocks are spread out underwater in such a way, giving the impression of a city layout. Boulder City is a deep and expansive dive site where the shallowest of boulder lie around 12m and the deepest at 40m with gaps of 30-40m between the 3 main pinnacles, stretched out on a sand bottom.

Anemone coral

The boulders are generally smooth with few corals although the surface area of the boulders is covered with soft coral like the stunning fluorescent pink Anemone Coral. Golden gorgonian fans and sea whips feed in the currents at the sides and in the cracks of the boulders.
Boulder City is a great searching site, looking in crevices and finding colourful marine life.

Currents

Boulder City is an exposed, deep dive site and currents can be strong but for this reason it attracts bigger fish such as whale sharks and manta rays, especially late in the diving season. The dive starts deep and gets gradually shallower as you work your way in and around the rocks in an S-pattern route.

Where to descend depend on the currents but on different sides on the site mooring lines will help you to descend and ascend which is recommended. The depth of the sand bottom at 35-40 meters is generally too deep to follow the whole dive. Instead try to stay close to or behind rocks and keep an eye on your decompression time.

Excellent visability

Visibility is normally excellent, especially during the stronger currents, so if something large swims by, there’s a better chance of seeing it! Reef sharks and smaller rays can usually be found out on the sand which surrounds the rocky dive site. In the deeper sections, there are many red and white whip corals. Here you are likely to spot small schools of Oriental sweetlips, blue-lined snapper, barracudas, grouper, triggerfishes, parrotfish and filefish. Other sights to look out for include Napoleon wrasse, turtles, and trevallies hunting swirling schools of glassfish.

Nudibranch

The abundance of algae growth here attracts plenty of grazers, including nudibranchs.
Nudibrachs are one of the most colourful creatures on earth and some divers are explicitly passionate about them. To avoid their predators some species can mimic their surroundings while others have intensely bright and contrasting colours to make them seem suspicious or poisonous. They vary in adult size from 4 to 600 mm. Nudibranchs are often mistakenly called sea slugs.

Unicornfish

There are masses of unicornfish, butterflyfish and angelfish happily feeding away. Sea urchins can be found wedged into the cracks, along with lionfish, scorpionfish and large moray eels. Scorpionfish always seem to hang around. Longfin batfish, black damsels and fusiliers are likely to accompany you on your safety stop.
Enough marine life to get underwater photography lovers really excited.

On the western side of Similan Island 5 Tuna Wreck lies just beyond the reef edge at 28 meters at top of the wreck. This side of the island is called Hideaway Bay.
Anita’s Reef is an easy dive site with gentle currents, making it an ideal check-out dive on a Similan liveaboard cruise.

All about the dive at Similan islands dive site Anita’s Reef

Anita’s Reef offers both reef and boulders. Add a wreck and a stunning bommie covered in life to make this site an amazing underwater landscape and a great dive.
Most divers start at the buoy south of Island 6 or at the shallow gap between Island 5 and 6 and swim southward to ‘Hin Muam Deaw” In this area some of the fish life you can expect to see here are lionfish, the colourful Oriental sweetlips and the gorgeous but less commonly seen clown triggerfish.
The coral bommies are covered in soft tree corals and sea fans that hide longnose hawkfish. These dendronephthya coral, in shades of golden brown and purple are the ideal hideouts of glassfish and juvenile fish. If you keep watching you’ll see bluefin trevally darting in and out swiftly as they hunt the smaller fish.

Hin Muan Deaw

The highlight of this reef “Hin Muan Deaw” is a delight to swim around; it contains a wide range of hard and soft corals and a delightful amount of marine life including a good range of reef fish, shrimps and reef crabs, ghost pipe fish as well as stunning nudibranchs. Huge shoals of glassfish are constantly seen around it. Don’t be surprised if the rock takes up most of your dive time on the site, being so excellent for micro-photography. The rock is also a fantastic night dive.
The rest of the dive is a nice reef dive. On your way more south-westward are often hordes of spotted garden eels on the sandy bottom and blue-spotted (Kuhl’s) stingrays buried in the sand. Here you can also see a type of filefish called a blue blanquillo as well as plenty of sea cucumbers. Look closely and you may be lucky enough to spot a whitepatch razorfish.
You can finish on the south west tip which consists of a series of giant boulders with a nice channel to surf through. This area is also known as Barracuda Point, although schools of barracuda are not that common any more.

Tuna Wreck

For a second deep dive nearby, Tuna Wreck lies just around the corner, on the west of Island 5. In 2003, the Similan National Park authorities sank a 30m fishing boat south west of Island 5 to create a new dive site known as Tuna Wreck. The wreck is marked by a buoy and sits on a sandy seabed just beyond the outer edge of the reef, with the depth varying from 28m meters, down to the deepest point at 40 meters.

You can visit Similan islands diev site Anita’s reef on a Similan islands liveaboard trip or Similan islands diving daytrip.

Dive at Boulder city reef on one of the next dive trips

MV Lapat
2 Days – 1 Night Liveaboard Trip

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Manta Queen 7
4 Days Liveaboard Trip

MV Andaman
3 or 4 Days Liveaboard Trips