Explore Richelieu Rock
The beautiful Andaman Sea that surrounds the Similan and Surin Islands is a world-class diving destination near Phang-nga province.. It’s in the heart of Thailand’s rich tropical ocean that is teeming with vast volumes of diverse marine life of all sizes. The area boasts iconic dive sites, including Koh Tachai and Koh Bon, but the one that towers above all is Richelieu Rock. Having been referred to in the past as a “whaleshark magnet”, this exciting site is a must for those who are on the hunt for the ocean’s largest fish.
Deep sea upwellings and currents bring in nutrient-rich waters, allowing massive plankton blooms which in turn attract an array of fish, and of course, the much-loved manta ray and whaleshark. This horseshoe-shaped island has much more on offer, including shoaling fish, a massive range of reef fish, colorful hard and soft corals, and lots of macro critter action.
As it’s a large dive site with depths varying from 5-35 meters, you can dive it multiple times and each will feel like a different dive. This in addition to its prolific marine life makes it a favorite location for day trips and liveaboard safaris.
If staying on a boat isn’t your thing, fear not, for dive centers and resorts, particularly from Khao Lak, also send day trips to this area, though do be aware of long travel times. You may even be able to dive Richelieu Rock as part of a dive course, depending on sea conditions.
Entry is normally on the southwest corner, where you’ll continue along the east side or simply follow the contours of the pinnacle. It can experience current as it’s exposed to open ocean, so it may be better suited to experienced divers or those at an intermediate level. It’s recommended to have a minimum of an open water certification, and dive operators normally prefer you to have experience diving in currents. Make sure you pay attention to your dive guide, not only due to possible currents, but also because the site can be quite busy throughout the high season, as it beckons divers from all around the world. To avoid the most crowds, try to dive Richelieu Rock very early in the morning before the masses arrive, or in the evening when they’ve already departed.
The best Months do dive in Richelieu Rock
The area, including the Similan and Suriin Islands, can only be dived from October until early May, while weather and ocean conditions at their best. It’s also the season when liveaboards are in abundance, and are easy to find.
February to April is the best time to see whalesharks and manta rays, though it’s possible to spot them all year. March and April can see reduced visibility due to plankton blooms, but this potentially means more pelagics. It’s also the driest season, with sunnier skies and calmer seas, making it the best period to dive here.
Visibility is usually good, ranging from 15-35 meters all year, and the water is just as welcoming, ranging between 27°C-30°C, however occasional thermoclines can cause brief lows of 25°C.
It’s important to be aware that the dive sites in this area are closed from May to early October due to rougher seas in the monsoon season, so make sure to visit outside this time.
Top Richelieu Rock Dive Sites
1. Richelieu Rock (Main Pinnacle)
This horseshoe-shaped pinnacle is famed for its rich biodiversity. Divers may encounter whale sharks, harlequin shrimp, seahorses, barracuda, and schools of snapper. It is an advanced scuba site with currents and deep drop-offs, and it lies within the Surin Islands Marine Park.
2. East Ridge (Richelieu Rock)
Located on the sheltered side of the rock, East Ridge offers colorful soft corals, cuttlefish, lionfish, and ghost pipefish. It is suitable for intermediate to advanced scuba divers. The site is known for calmer conditions and makes an excellent second dive.
3. West Wall (Richelieu Rock)
This steeper, deeper side of the rock features dramatic walls and swim-throughs, attracting trevally, moray eels, and the occasional manta ray. Due to depth and surge, it's best for advanced scuba divers looking for thrilling topography and pelagic species.
4. Surin Islands (Koh Torinla) – Freediving possible
Just north of Richelieu Rock, the Surin Islands offer easy scuba and freediving on healthy reefs with clownfish, reef sharks, and turtles. Protected within the national park, Koh Torinla features gentle slopes and excellent visibility, ideal for all levels.
5. Koh Tachai Pinnacle
Often included in liveaboard routes from Richelieu Rock, this site hosts leopard sharks, barracuda, and batfish. Strong currents and deep formations make it suitable for advanced scuba diving. The submerged boulder landscape creates dramatic underwater scenery.