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Diving Thailand – Dive Sites Thailand – Scuba Diving Similans
Name Richelieu Rock Similans
Depth 5-37m
Vis 5-40m
Water Temp 26-30c
Level Intermediate+
Our Rating 5 Stars
Best Time to Visit October to May
GPS 09-21-771N 98-01-324E
  Map of Similan Islands
Richelieu Rock

Richelieu Rock is the highlight of any dive trip in Thailand and is reputed to be the best dive site within the combined Similans and Surin Islands National Marine Park. It's a relatively small dive site, and is at times overcrowded with divers all vying to see the huge spectrum of marine life living here. Indeed, some species here are native only to this one dive site. Richelieu Rock is sometimes subject to strong currents and thermoclines. On a good day the vis can be as good as 40 metres. On a bad day it can be as low as a disappointing 5 metres. Having said that, even in bad vis it's an outstanding dive.          

Expect to be shown Harlequin Shrimps, Tigertail Seahorses, Ghost Pipefish, Stonefish, Tomato Clownfish, a vast array of Nudibranchs, schooling Jacks, Barracuda, Pipefish, Frogfish, Zebra Morays, Batfish, Lionfish, Indian Walkmans, occassional Manta Rays, and the fish the site is famous for - Whalesharks! Richelieu Rock undoubtedly has more visits from Whalesharks than any other dive site in Thailand, although Hin Daeng and Hin Muang close to Koh Phi Phi come a very close second. The season for Whalesharks used to be slated as March to April, but these days they make appearances at dive sites within Thailand all year round, and thankfully, after fewer sightings year after year, they seem to be making a gradual comeback.


The decline was blamed on fisherman in some countries like Bangladesh, India and the Philippines killing the Sharks, primarily for their fins. Thankfully, some of these communities are now promoting Whaleshark eco tourism as opposed to killing the largest fish the sea has to offer.

Richelieu Rock is comprised in the shape of a horseshoe. Small critters are found inside and out. It is a must to go with an experienced dive guide here if you want to see all the dive site has to offer. It's virtually impossible to find the smaller rarities like the Harlequin Shrimps, without a dive guide to show you where they are. The site is blanketed with purple soft corals and colourful sea fans making this site a photographers dream. It's good to plan at least two dives here, as there is so much to see. Take your time to explore all the nooks and crannies and be delighted at almost every peek inside. If you hear divers tank bangers, rattles and other alerts being sounded frantically, it usually signifies the appearance of a Whaleshark, or possibly a Manta Ray.

Spend a dive here on the north eastern outer wall of the horseshoe. This is the best spot to see the Whalesharks. Just hang in the current there waiting and if you're lucky a huge brown spotted form will emerge into view from the blue. They tend to cruise up and down this wall in a figure of eight pattern. Don't bother chasing them, it's impossible due to the currents and they will effortlessly outpace you as you chew through your air. More often than not they will circle around for pass after pass. They can be pretty impressive from anything from just a few metres up to more than 12 metres. Please remember, if you're lucky enough to be graced by the appearance of a Whaleshark, not to be tempted to touch it or ride it. First of all, you will scare it off much to the annoyance of other divers.  Secondly, you can actually harm a Whaleshark by touching it, by taking off a protective layer from its skin that protects it from bacteria and parasites. Touching a Whaleshark can kill it!

There is an incredible amount of boat traffic at this dive site, so remember to use a surface marker buoy when surfacing after your safety stop.