Richelieu Rock

Richelieu Rock, Hin Plo Naam in Thai, is a limestone pinnacle rising from about thirty-five metres to the surface, which it breaks at low tide, in the Andaman Sea some 18 kilometres east of the Surin Islands and 45 from the mainland, shaped as a horseshoe and standing alone in open water - which is why it concentrates life. It is consistently rated among the best dive sites in Thailand and among the better ones in Southeast Asia: the rock is covered in purple soft coral and anemones, with schooling barracuda and trevally, seahorses, ghost pipefish, harlequin shrimp and frogfish on the walls, and it is one of the best-known places in Thai waters for whale sharks, which pass most often from February into April. It is a dive site only - there is no landing, no day-trip option and no snorkelling infrastructure; access is by liveaboard from the Andaman ports. The marine park closes from mid-May to October. The name is that of Admiral Richelieu of the Royal Thai Navy, who first surveyed these waters, and appears on navy charts from the early 1900s - not, as often told, a name given by Jacques Cousteau for the cardinal's red robe. Currents can be strong and it is not a beginner site in poor conditions.

The landscape

• The horseshoe pinnacle - rising from thirty-five metres and breaking the surface at low tide.
• The soft coral - purple cover across the rock with anemones and macro life.
• The whale sharks - most reliably from February into April.
• The liveaboard-only access - no day trips and no landing.

When to go

February to April for the best whale shark chances; the marine park season runs November to mid-May and it is closed the rest of the year.

Practical notes

Liveaboard only - there is no way to visit for a day. Whale sharks are never guaranteed. Currents can be strong and the site is unsuitable for inexperienced divers in poor conditions. The park closes from mid-May to October.

Nearby

The Surin Islands are close by sea; Khura Buri and Khao Lak are the mainland departure points.

Key facts