Big Blue Dive Site Guide
Richelieu Rock
Day Trip Diving
Our Similan diving day trips will resume in November 2025
Location
14 km east of Koh Surin Nua
Skill Level
Intermediate to advanced
Depth
0 - 30m
Currents
Weak to strong
Topography
Limestone pinnacles that form a croissant shape when viewed from above, shallower on the South side and deeper on the Northern side. Scattered pinnacles surrounding the main rocks with larger pinnacles South-east and on the Northside. Bottom composition is mainly rubble and sand.
Highlights
There's something for all divers at Richelieu Rock: amazing macro life including tigertail seahorses, ornate ghost pipefish and harlequin shrimp, huge schools of barracuda, giant trevally, rainbow runners and long-nose emperor fish, abundant soft corals and anemones, and if you're lucky the occasional whale shark.
Tips
Take your time diving Richelieu Rock. It is not a huge dive site but the amount of life around the rock is staggering. There's so much to find diving slowly, checking out all the cracks and caves in the limestone rock and exploring the scattered pinnacles around the main rock.
Photography
There's so much life at Richelieu Rock you can chose your favourite shooting styles. There's magnificent macro life and cool critters if that's what you like to shoot. There's also colourful coral vistas that teem with reef fish and huge schools of pelagic fish if you like wide-angle photography. As you will have a least two dives at Richelieu some photographers opt for different lens on different dives.
Briefing
Richelieu Rock is usually the highlight of our Similan liveaboard trips and our speedboat weekly schedule. Weather permitting the Blue Dolphin liveaboard will always plan three dives there, one of them a sunset dive and our speedboat daytrip is two dives at this famous rock, four times a week. This gives us a lot of time to explore the dive site fully and our dive briefing for Richelieu Rock spans the two or three dives there.
On our first dive at Richelieu Rock, after descending down the descent line, we will head anti-clockwise around the Northern, deeper side of the rock. If the dive site is busy, which it often is, there are some scattered rocky pinnacles a short swim from the main rock where we can avoid other divers. These smaller pinnacles are covered in soft corals, surrounded by glass fish which are prey to the huge schools of pelagic fish that roam around the site. Ascending for the second portion of the dive we head around to the Southern side of the rock. We refer to this as inside the rock or on the shallow side of the rock as we are now diving in the inside part of the croissant shape. This is ideal as the rock and marine life continue almost to the surface so even on our safety stop we can be dazzled by the fish and coral life at Richelieu Rock.
Our second dive at Richelieu Rock starts again at the descent line, then this time heading in a clockwise direction around the main rock covering the deeper parts on the Southwest croissant tip and then continuing around the shallower parts of the Northern side. By the end of the second dive you will have seen the best features of the dive site. If you are on our diving day trip it’s now time to head back to shore. For our liveaboard divers there’s one more special dive at Richelieu, our legendary sunset dive.
For the third dive of the day at Richelieu we wait until the sun is lower in the sky and conditions are darkening underwater. This is one of the best times of the day to catch some real hunting action especially if there’s some current to really add some spice to the dive. There is no set route for this dive, it’s just your dive guide’s instinct where to find the most activity. Our sunset dive at Richelieu Rock is often the best dive of the day and as it’s Richelieu Rock, likely the dive of the trip. Well maybe the sunset dive at Koh Tachai was special too!
Fish and Other Species Found at Richelieu Rock
Red Sea Fan
Peacock Mantis Shrimp