Boulder City
Conditions & tides
Scored by DiveConnect's site-physics model
Marine forecast via Copernicus Marine. Score is a rule-based guide from swell/wind vs. the site's exposure — always dive your own assessment.
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About this site
Boulder City is a submerged granite outcrop in the Similan Islands of Thailand, lying about 200 metres south of Koh Payan. The site is completely submerged and marked by two mooring buoys, one at the north end and one at the south.
The north line takes you to 20 metres and the south line to 30 metres, and the shallowest point of the site is 16 metres. Large granite boulders, some bigger than a house, lie jumbled around a flat sandy bottom, with swim-throughs between them. Gorgonian sea fans, tree coral and whip corals grow here.
Currents can be strong, which brings fish-filled dives with schooling snappers, fusiliers and barracuda. The site is only 400 metres from Shark Fin Reef, so look out for humphead parrotfish and napoleon wrasse as well. Sharks, Jenkins and blotched fantail rays turn up on the sand, with octopus, moray eels and angelfish around the boulders.
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There is a large amount of plankton around the site, so looking up and around is worth your time. It is known for manta ray and whale shark sightings.
Marine life here
Confirmed by our research team, reported by independent divers, or observed nearby via iNaturalist — each entry is labelled with its source.
Guam ScorpionfishScorpaenodes guamensisReported here · unconfirmed
Moon WrasseThalassoma lunareReported here · unconfirmed
SnapperSnapperReported here · unconfirmed
FusilierFusilierReported here · unconfirmed
BarracudaBarracudaReported here · unconfirmed
ParrotfishParrotfishReported here · unconfirmed
Napoleon (humphead) wrasseNapoleon (humphead) wrasseReported here · unconfirmed
OctopusOctopusReported here · unconfirmed
AngelfishAngelfishReported here · unconfirmed
Manta rayManta rayReported here · unconfirmed
Whale SharkRhincodon typusReported here · unconfirmed
Bumphead parrotfishBumphead parrotfishReported here · unconfirmed
Moorish IdolZanclus cornutusObserved near here · iNaturalist
Blue LinckiaLinckia laevigataObserved near here · iNaturalist
Tawny Hermit CrabCoenobita rugosusObserved near here · iNaturalist
Indo-Pacific Sergeant MajorAbudefduf vaigiensisObserved near here · iNaturalist
Durable tips from divers — access, hazards, marine life, facilities. For day-of conditions, use the report tool in the conditions card above.
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