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 dive site on the southeast coast of Island No.3 in the Similan Islands. A huge array of gigantic boulders lies scattered over white sand.
The tops of the boulders sit at 12 to 18 metres and their bases drop to between 30 and 40 metres. Most of them are covered in tube corals of many colours, giant gorgonian sea fans swaying in the current, and staghorn coral. The crevices and holes hold Dancing Durban shrimps, pipefish and red fire gobies, while Napoleon wrasse and humphead parrotfish cruise around the rocks.
Manta rays, eagle rays and great barracuda sometimes show up in the blue. Strong currents run across the site, so divers stay close to the rocks to avoid swimming against them in mid-water.
Marine life here
Confirmed by our research team, reported by independent divers, or observed nearby via iNaturalist — each entry is labelled with its source.
Eagle rayEagle rayReported here · unconfirmed
BarracudaBarracudaConfirmed present · 2 independent sources
Eightband ButterflyfishChaetodon octofasciatusReported here · unconfirmed
Argus WrasseHalichoeres argusReported here · unconfirmed
Copperband ButterflyfishChelmon rostratusReported here · unconfirmed
Viola Land Hermit CrabCoenobita violascensReported here · unconfirmed
Pastel-green WrasseHalichoeres chloropterusReported here · unconfirmed
Boring Giant ClamTridacna croceaReported here · unconfirmed
Bengal SergeantAbudefduf bengalensisReported here · unconfirmed
Black Longspine UrchinDiadema setosumReported here · unconfirmed
PipefishPipefishReported here · unconfirmed
Napoleon (humphead) wrasseNapoleon (humphead) wrasseReported here · unconfirmed
NudibranchNudibranchReported here · unconfirmed
Bumphead parrotfishBumphead parrotfishReported here · unconfirmed
Manta rayManta rayReported here · unconfirmed
Banded Sea UrchinEchinothrix calamarisObserved 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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