Boulder City

Similan Islands dive site

Location: 3 km off the east coast of Koh Payan (Similan Island #3)

Depth: 8-50 m

Type: Granite Boulders

Level: Intermediate to advanced. Strong currents


Boulder City forms a chain, with Shark fin reef to the north, of submerged boulder formations. It is often the last dive site dived on a liveaboard trip before the cruise back to the mainland. That’s because of it’s southern location in the Similan Islands group.

Dives at Boulder city can be challenging because the site is exposed and currents are often strong. There are mooring lines which may be used for descent and safety stops.

Boulder City is characterized by large granite boulders stacked on top of even bigger granite boulders. These boulders provide a stunning underwater seascape. Because they are in open sea away from the islands they can attracted bigger fish such as whale sharks and manta rays.

Giant barracuda, dogtooth tuna and mackeral are also common as this dive site has many cleaning stations.

The boulders drop down below 35 m and a typical dives involves descending deep and then working your way back up, in and around the rocks, seeking protection from the current where necessary. The boulders are generally smooth with few corals although there are patches of soft coral and crinoid growth.

Seafans and sea whips feed in the currents at the sides of the boulders, sometimes blocking a divers route through a rocky valley. Sea urchins wedge themselves into the cracks. Lionfish and scorpionfish also like the cracks in the rocks as do moray eels. Grouper and parrotfish are always busy. Oriental sweetlips can be seen at home under small table corals.

Leopard sharks and whitetip reef sharks are seen in deeper areas. The eagle eyed diver may also be able to spot purple fire gobies. Longfin batfish will probably keep you company on your safety stop.

How to dive the Similan Islands

You can dive the Similan Islands by day trip from Phuket or Khao Lak, or by liveaboard. Liveaboards are ideal given the size of the area, the variety of dive sites, and the distance from the mainland.

A typical Similan liveaboard itinerary is 4 days 4 nights and also includes Koh Bon, Koh Tachai and Richelieu Rock. Shorter 2d1n or 3d2n trips are also available.

If you don’t mind longish transfers then Similan diving day trips with 2 dives run five days per week from Phuket.

The Similan Islands diving season is from 15 October to 15 May.


More Similan Islands dive sites


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