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Get the Most out of your Similan Diving experience

Similan diving, including Koh Bon, Koh Tachai and Richelieu Rock is the best Thailand scuba diving on offer. The topography of the dive sites is varied, the water is crystal clear and sometimes the Similan Islands can be full of surprises.


The diving season is from mid October to end of April!

From May to mid October the Similan National Marine Park is closed and entering within these months is illegal and also highly dangerous because of the prevailing weather conditions!


Join our unique Khao Lak diving day trips

On a traditional Thai longtail boat and dive the fascinating Boonsung Wreck




After a positive start to the 2014 to 2015 Similan diving season in October and November, great diving conditions continued well into December. Compared with the previous season, fewer divers visited the Similan Islands. Those divers that did make the trip out to this famous archipelago enjoyed uncrowded Similan dive sites and plenty of fish life.

Inclement weather conditions had an adverse effect on diving conditions over the peak season rush, as has become increasingly common in recent years. These unpredictable and disruptive conditions occurred between around the to the . Strong winds from the north caused high waves in the Andaman Sea, then caused a few trips to be cancelled and a drop in visibility around the Similan Islands, Koh Bon, Koh Tachai and Richelieu Rock.


The start of the new year saw conditions in the Similan Islands improve dramatically. The Andaman Sea calmed quickly and visibility improved, especially in the south. Similan liveaboard trips could once again visit all sites on their schedules.

The number of divers visiting the Similans at the time of writing (mid-January) are still down on last season’s figures. As we head into the best period for diving in the Similans in our six month season, this means that right now is a great time to visit, as the dives sites will not be overcrowded. However, in mid January the weather has still not truly settled into high season North East monsoon. Some days can see stronger winds with higher waves.

The visibility in the south Similan Islands is very clear at the moment, getting worse heading north as far as Koh Tachai. The visibility at Richelieu Rock can be a bit unpredictable, affected more by the prevailing conditions of the southern Mergui Archipelago in Myanmar.

With each passing full moon fish stocks are growing in quantity. Though the visibility at Koh Tachai and Richelieu is unpredictable, divers can be assured of seeing plenty of fish life. Koh Bon seems to be the most consistent Similan dive site so far this season with decent amounts of fish life and good visibility.


The 2013 – 2014 diving season saw a vast improvement in the coral life at the Similan Islands. Coral bleaching in 2010 effected many dive sites across S.E. Asia with the Similan dive sites being some of the worst hit in the entire region. New coral growth was observed in 2011 – 2012, yet this did little to improve the overall look and feel of the dive sites.

Strong prevailing northerly winds caused water temperatures to cool in the Andaman Sea at the end of 2013 and this had a dramatic effect on the Similans as a whole. Not only was there a rise in marine megafauna sightings, but there was also more rapid coral recovery; both were attributed to the cooler water temperatures. New coral colonies began to sprout on many Similan dive sites and existing new coral growth flourished.

The shallow waters around the islands had been the worst hit by coral bleaching, therefore, it was very positive to see a lot of the new coral colonies forming up to a depth of 5 metres below the surface. Some of the best dive sites to benefit from new coral growth are Christmas Point and West of Eden in the Similan Islands and the northern part of the reef at Koh Bon.

Strong northerly winds over new year have continued to keep water temperatures cooler and the coral recovery continues into 2015. Reduced visibility has not been so great for divers, but has been beneficial to the coral reefs. 2015 is a positive start for the continued coral recovery.



A great deal of focus has been put on whether 2014 – 2015 could live up to the latter half of the 2013 – 2014 Similan diving season. Last season saw whale shark and manta ray sightings rise dramatically. Since 2011 only a handful of whale sharks had been spotted each year. Early signs are very positive indeed. Several whale sharks were sighted at Richelieu Rock, Koh Tachai, Koh Bon and at Elephant Head Rock in the Similan Islands very early in the season. Sightings, though not in abundance have continued since then. (Read more about the sensational Similan Islands at the end of 2014 season here.)

Manta Rays typically migrate through the region from January to March, yet several were sighted at Koh Bon and Koh Tachai in November and December 2014. Although it is not uncommon to see Manta Rays early in a season, sightings were usually brief with one individual being observed from a distance. Up to four Manta Rays have been spotted on a single dive at Koh Tachai with some interacting with divers.

It might take several more years for the Similan Islands to see broader or even complete recovery, but there is definitely a more optimistic feeling so far, at the start of 2015.

With diving activities well underway conditions should only improve over the final three months of the season. With each passing full moon there should be a marked increase in fish stocks. Plus with fingers and fins crossed, the whale shark sightings will hopefully continue.

Adverse weather mainly due to climate change did hamper some trips in December, as has become more common over the past few years. Always be sure to check our weather updates and information before heading out to the Similan Islands.


Dive with a smile :)


If you are a novice diver, diving Similan Islands is often a wonderful experience. Many of the sites offer easy diving conditions, crystal clear water and the good chance to see firm favourites such as turtles, anemone fish, moray eels, stingrays, pufferfish, lion fish, batfish and occasionally larger pelagic species such as barracuda and trevally. If you include diving at Koh Bon which is often included in a weekly Similans schedule then there is a good chance to see Giant manta rays at certain times of the season. The diversity of dive site types is a strong point of the Similan Islands. Gentle sloping coral reefs form on the east side of the islands, while rocky reefs dominate the west sides. There are also a number of submerged pinnacles that form dramatic underwater seascapes and create adventurous dives through caves and swim throughs which adds appeal for more experienced divers.


If you are a more experienced diver or have already logged a lot of dives at some of the world’s great locations (e.g. the Red Sea) you may find similan diving not quite what you expected. Apart from notable Similan dive sites such as Elephant Head Rock, Christmas Point and West of Eden you will find the dive sites to the north of the Similan Islands more fitting to your experience level and expectations. Koh Bon, Koh Tachai and Richelieu Rock are more advanced dive sites and due to positioning and stronger currents offer a better chance to see larger marine life. Manta ray sightings that were previously declining, are now much more frequent at Koh Bon and Koh Tachai, especially between the months of January and March. Whale shark sightings are also becoming more common at Koh Tachai and Richelieu Rock with the occasional sighting at Koh Bon and even in the Similan Islands. Abundant soft corals and sea fans, coupled with large quantities of fish life and larger pelagic species, set Koh Tachai and Richelieu Rock in a much higher class of diving.

Do not expect to be alone at the Similan Islands. With all guide books, internet sites and local operators selling the Similan Islands as one of Thailand’s top destinations you will find the islands and dive sites crowded. Unless your Similan Island trip includes divers, snorkelers or beach lovers in one group, avoid trips to the Similan Islands offering all activities from only the one large vessel, otherwise you will be snorkelling at dive spots or diving snorkelling spots whilst feeling the tremendous time pressure to complete your planned day! Thailand Dive and Sail recommend trips that separate their diving and snorkelling activities, with fast transfers to the Islands and also offering weekly schedules that include the better diving at Koh Bon, Koh Tachai and Richelieu Rock. Boats offering only a Similan Island and Koh Bon weekly schedule are not offering you the best of the Andaman Sea area.

Interested in diving with a highly experienced and knowledgeable team in the Similan Islands?


If you plan your similan diving activities to be conducted as day trips, Thailand Dive and Sail recommend the following trips for the scuba diver who wants to get the most out of their limited time in Khao Lak.

A day trip to Richelieu Rock must top the list. This is by far Thailand’s premiere dive site. We offer a fantastic speedboat day trip to Richelieu Rock. Diving from our speedboat limits the number of divers jumping in at the same time whilst every attempt is made to jump in at different times from the busy live aboard schedule operated at Richelieu. Fast transfers to and from Richelieu Rock means a later pick-up time in the morning and an earlier arrival back at you hotel.

A day trip to either Koh Bon or Koh Tachai to hopefully dive with larger marine species such as Manta Rays. Thailand Dive and Sail offer a speedboat trip which visits both of these top destinations in one dive day.

Check our new revisied Similan day trip diving information.

A local dive trip to the amazing Boonsung Wreck, just off Khao Lak’s coastline. Thailand Dive and Sail offer a true Thai diving experience to the wreck. Our traditional longtail boat departs directly from one of the areas most beautiful white sandy beaches and takes a mere 30 minutes to reach the dive site. Although the visibility is often not as clear as the islands further out in the Andaman Sea, the quantity and quality of the fish life there is surpassed only by Richelieu Rock. Experience has shown us that the wreck is regularly quoted as one of the best dives on offer.

During peak season 2014 – 2015 Thailand Dive and Sail will operate a more private, intimate speedboat trip to Richelieu Rock every Monday. From January 2015 when the Manta Ray season really kicks in we will also be offering Manta research trips to Koh Bon. These trips are purely focussed on Manta ray education, conservation and you will have the direct opportunity to contribute to Manta ray research through photographic ID. Please contact us if you would like more details of either of these trips.

If you have the time, by far the best way to maximise your dive time in the area is on a Similan Island Liveaboard. You get the chance to see the Similan Islands at quieter times of the day and spend some time on the beaches there before heading north to the better dive sites. Most live aboard trips are four day/four nights although Thailand Dive and Sail also offer flexible two, three, four and five day trips. Read more about Similan liveaboards.