A Guide to Diving the Similan Islands

A Guide to Diving the Similan Islands

For a few seasons Becks and I worked as guides and instructors out on the Similan Islands. We’ve logged thousands of dives out there and know the place like the back of our hand. If you are heading out there, don’t miss our guide to diving the Similan islands.


Thailand boasts some pretty good diving and having dived both sides of Thailand is was unanimous for us that the Similan Islands is our top dive pick for Thailand.


Lying off the south west coast of Thailand in the Andaman Sea are 9 islands. ‘Similan’ derived from the ‘malay’ word meaning 9 Islands are easily accessible from either Phuket or Khao Lak (84km North of Phuket) either by day boat or live-a-board. The season there runs from Nov-May.


We recommend you take a live-aboard out from one of the many dive centres in Khao Lak for at least 4 days. Take your time before booking to read the trip itinerary and be sure to include Richelieu Rock, Koh Tachai and Koh Bon in your chosen trip.


A Guide to Diving the Similan Islands, Thailand
Similan Islands – Photography by Leigh Dunne.

Our Similan Island Top Picks


Koh Tachai:

Synonymous with currents, this underwater pinnacle has the potential to bring loads of action. Only to be dived early morning or at sunset (sunset is my pick), I have many a times spent the entire dive holding the outer rock enjoying the frenzied GT’s hunting between the schooling barracuda. Another hot spot for potential manta fly-bys – RARE.  Koh Tachai also boasts a beautiful underwater scene. Nice colour, big boulders and loads of seas fans, it has the potential for an epic dive. Orangutan crabs, crinoid shrimp, ghost pipefish can be snapped here. Leopard sharks and whitetips in the early morning can be found of the western plateau at 30m+.


Koh Bon:

Lying 17 nautical miles north of Island number 9 , Koh Bon is renown for it’s oceanic mantas. Colourful coral doesn’t exit here (other than the initial wall which host a small display of soft corals and loads of ‘blue dragons’), it was bombed out years ago. Don’t let this put you off. Leopard sharks and white tips can be found here roaming the 30m mark in decent current. Napoleons and trevally’s circle the shallower coral bombies. Cuttlefish, and octopus are often found displaying colourful mating rituals and vibrant displays and we have also found soft shell cowries on the walls.. However the reason you come to Koh Bon is for the oceanic manta cleaning station. Best months for this are Jan-May but to be honest I have found mantas all season round. It’s just luck.


A guide to Diving the Similan Islands, Thailand
Leopard Shark. Photography by Leigh Dunne


Richelieu Rock:

Richelieu is the premier dive site in Thailand but be warned, your dive guide will be on a set course trying to fit everything in. Fighting your No Deco limits you may be whisked around to the tiger tail seashore, the harlequin shrimp, bent stick pipefish, pineapple fish, stonefish, stargazer, ornate ghost pipefish….  and on and on. There is always loads of macro to be seen amongst the colourful purple corals but also loads of divers. Be prepared for queuing for photo’s… Obviously we are not guaranteeing all of these things but it gives you  good example as to what you can find here. Having nailed this review honestly, I will admit on a stunning day, with gorgeous visibility, this dive site is second to none!


NW- In most guide books Richelieu is frequently visited by whale sharks. In over 300 dives on Richelieu itself neither of us had witnessed the mighty shark.


On a 4 day live-a-board trip, the underwater landscape will change many times. The sloping reefs and sandy bottoms of ‘the south islands are perfect for new divers. Garden eels and the symbiotic gobie and partner shrimp and plentiful, whilst the blue spotted stingrays lie motionless in the sands. Colourful coral mounds are frequent yet abundant with glass fish, greedy trouts and nudibrachs. Keep your eyes out for juvenile rock-mover wrasses, sea moths razorfish, comet fish and oriental sweetlips are often hiding out in the sand or under small rocky ledges. Manta fly by’s are rare but it’s always worth keeping your eye out.


The impressive granite boulders which form ‘Elephant Head Rock’ and Turtle Rock’ in the north are unique. The house-size boulders which can be seen protruding the top of the ocean continue deep below the surface.  Stacked rustically on top of one another (as if on purpose), the gaps between the boulders create long swim throughs. Not cavernous, these passageways are interrupted by curious rays of sunshine finding their own way through the granite maze. Endless routes and pathways be sure to go with a guide who knows the ins and outs. Keep an eye out for ornate ghost pipefish in the cracks as well as lazy white tips lying in the depths. Again we have seen mantas on all these sites – so always keep an eyes in the blue.


Tigertail Sea Horse. Photography by Leigh Dunne.
Tigertail Sea Horse. Photography by Leigh Dunne.


Lastly, but probably most excitingly; the energetic underwater pinnacles of the north.  The  underwater pinnacles are always on a live aboard trip list for obvious reasons. With a 15m clearance between surface and pinnacle in open ocean means current – sometimes. Hitting these dives after full moon means fishy Mcfish! Barracuda, GT’s and snappers all frenzied upon sunset with a spectacular display of an underwater orchestra.  The colour on these sites are also second to Richelieu with some boasting bright yellow soft corals completely swallowing an entire 50m pinnacle. Eagle rays, leopard sharks, Mantas and rarely whalesharks are all locals to these sites.



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Written by

Prue Sinclair is a twenty-eight year old Aussie who for the past seven years has been exploring the furthermost reaches of the World. Living anywhere but her homeland, she now resides somewhere in the UK where she writes about the adventures of her Ultimate British Road Trip. Her message is simple: You can get anywhere on any budget, you just need to think outside the box. You can trust she’s finding her way to somewhere lesser-known and writing a ‘How To’ guide.


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Hi we're Prue and Becks, travel writers and photographers who have been travelling the world together since 2012. Without taking ourselves too seriously, we divulge the lesser known, out of the way places and give you the tools to replicate it. Want to know more? Click on our pic.