Samaesan
Conditions & tides
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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
Samaesan is an open-ocean technical dive site located between Koh Samaesan and Koh Chuang in the Gulf of Thailand, reaching depths of 85 to 100 metres. Known informally as the "Silty Black Hole of Death," it is the deepest and most dangerous dive site in the Gulf of Thailand and has been recognised among the world's most extreme dive sites. The site was formerly used as a military ordnance dump and the seabed contains unexploded ammunition.
The terrain is open ocean, dropping to a maximum of 100 metres, with no reef or wreck structure. Poor visibility and darkness at depth are the norm, and the site sits directly in a busy commercial shipping lane, adding a significant surface hazard.
Conditions at Samaesan are severe and highly demanding. Currents are extreme and unpredictable, with strong down currents and vortex effects reported. Diving is only viable at slack water during the season from November to April. Water temperature ranges from 27 to 30°C. Nitrogen narcosis and oxygen toxicity are real risks at the depths involved, and the combination of darkness, poor visibility, unexploded ordnance, and heavy tanker traffic makes this one of the most hazardous dive sites in the region.
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Access is by boat, approximately 30 minutes from the Samaesan area. The site is suited exclusively to experienced technical divers with appropriate trimix training and certification; it is not appropriate for recreational diving at any level.
Marine life here
Confirmed by our research team, reported by independent divers, or observed nearby via iNaturalist — each entry is labelled with its source.
Black-margined NudibranchDoriprismatica atromarginataReported here · unconfirmed- Synaptula reticulataReported here · unconfirmed
Scissortail SergeantAbudefduf sexfasciatusReported here · unconfirmed
Tryon's HypselodorisHypselodoris tryoniReported here · unconfirmed
Red SquirrelfishSargocentron rubrumReported here · unconfirmed
Varicose Wart SlugPhyllidia varicosaReported here · unconfirmed
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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