The Pinnacle is the summit of Richelieu Rock, the top of a seamount that rises from over 35 m of open Andaman water to within 2-3 m of the surface at low tide and is close to invisible at high tide. Purple soft corals cover the slopes, and the same open water that makes the rock hard work brings whale sharks and manta rays past it in season.
Also known as Hin Plo Naam.
Where it is and how deep
9.3633° N, 98.0219° EPublished position for this site.
The dive
Boats work an anchor line here, and Wikivoyage's standing advice is to hang on to it going down and coming back up: the rock stands alone in open water and current at the surface can be moderate to strong. The summit itself only breaks within 2-3 m of the surface at low tide and is close to invisible at high water, so the line, not the rock, is your reference on the way down.
From the top the flanks fall away on every side toward a base at over 35 m, with the site's maximum around 33 m. Work down one side, out of the current where you can, following the purple soft corals that cover the slopes. A torch earns its place once you are off the top, because what the rock is known for is small and well hidden: frogfish, nudibranchs, harlequin shrimp, ghost pipefish and seahorses.
Save the second half for the shallows. The summit is the shallowest ground on the site, and anything passing in the blue is easiest to see from there - Wikipedia gives February to April as the best window for large pelagic species, whale sharks and manta rays included. Come back up the anchor line where you can: the site is open and unprotected, and exiting the water can be demanding when the waves are up.
Background
Richelieu Rock sits inside Mu Ko Surin National Park, a marine protected area open 15 October to 15 May that may close earlier in bad weather. The name is often credited to Jacques-Yves Cousteau, but the attribution is disputed: his 1989 Andaman expedition reached only as far north as Koh Bon while he waited on a Myanmar permit. The likelier source is General Richelieu of the Royal Thai Navy, the first person to complete a hydrographic survey of the Andaman Sea.
Marine life and season
- Whale sharks
- Manta rays
- Frogfish
- Nudibranchs
- Barracuda
- Macro critters
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Good | Prime | Prime | Prime | Off-season | Off-season | Off-season | Off-season | Off-season | Off-season | Good | Good |
Season follows Richelieu Rock: Surin park closes mid-May to mid-October; whale sharks are most reliable February-April when plankton blooms peak.
Know before you go
- Current runs moderate to strong and is strongest at the surface; use the anchor line on descent and ascent rather than swimming against it.
- Scorpionfish and stonefish on the rock are very well camouflaged, so look before you put a hand, knee or fin anywhere.
- Exiting the water can be demanding when waves are high; stay on the line and wait for the boat rather than swimming across open water to it.
Photos from The Pinnacle
luluchouette · CC BY 4.0
Questions divers ask
How deep is Richelieu Rock?+
The summit comes to within 2-3 m of the surface at low tide and the ground around the rock lies at over 35 m. Wikivoyage gives the dive site's maximum depth as about 33 m.
When is the best time to see whale sharks at Richelieu Rock?+
Wikivoyage records common sightings of whale sharks and manta rays during the season, especially at its beginning and end, and Wikipedia names February to April as the best time for large pelagic species. The national park is open 15 October to 15 May and can close earlier depending on the weather.
Do you need to be an advanced diver for Richelieu Rock?+
Dive The World rates the site intermediate to advanced. It is an open, unprotected pinnacle in open water with moderate to strong current and a maximum around 33 m, and the recommended descent and ascent are hand over hand on the anchor line.
Sources
- Richelieu Rock — Wikipedia
- Diving in Thailand — Wikivoyage
- Diving in Thailand/Richelieu Rock — Wikivoyage
- Richelieu Rock, Koh Bon & Koh Tachai — Dive The World
- Richelieu Rock dive site — Divezone
Photo credits
- Yellow tiger tail seahorse clinging to orange soft coral at Richelieu Rock by TimSC, CC BY 4.0, via Wikimedia Commons
- Pickhandle barracuda pair cruising in open blue water by luluchouette, CC BY 4.0, via Wikimedia Commons
In The Logbook
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- How long should a surface interval be?Body & health · 8 min read
- Where to dive with whale sharks, month by monthBig animals · 16 min read
Similar dives elsewhere
A current-swept pinnacle from 30 m to within 5 m of the surface
Offshore granite tower where barracuda and jacks school in the blue
Mantas and a swirling barracuda vortex over a current-swept plateau
Unmarked deep pinnacle where mantas and leopard sharks turn up