Richelieu Rock

Richelieu Rock is a horseshoe-shaped limestone pinnacle rising from about 35 m to just under the surface, famed for dense soft-corals and colorful sea fans and for a mix of macro critters (seahorses, frogfish, harlequin shrimp, pipefish) and large pelagics (whale sharks, manta rays, barracuda, trevally) that are considered major attractions. The reef and surrounding bommies are covered in soft coral gardens, barrel sponges and anemones, with undercut ledges, swim-throughs and overhangs that concentrate macro life. Access is by boat only, located offshore in Surin National Park via mooring lines. Depths range from sheltered shallows around 5 m to about 30–35 m on the outer edges. Visibility is usually good, often 10–30 m, but can drop during plankton blooms; typical water temperatures are warm, in the high 20s °C. Currents are commonly moderate to strong, generally flowing north-south through the horseshoe, so many dives are drift-style; divers commonly descend on the eastern mooring line and follow channels and walls around the outside. Entry is by boat only and the site is open during the national park season (roughly mid-October to mid-May). Strong currents, open-ocean remoteness and depths to ~35 m mean the site is best suited to experienced divers comfortable with drift diving; follow downlines, boat briefings and perform safety stops away from the rock because of boat traffic, and note the park can close unexpectedly in deteriorating weather.