It is generally accepted that The Similan Islands offer Thailand’s best diving experiences. There are approximately twenty excellent dives sites, including deep and challenging as well as those which can be dived by complete beginners. However, it is also agreed by most that Richelieu Rock, just to the north of The Similans, is the best single diving site in the country. While Richelieu Rock is near The Similan Islands, and dive cruises often visit both, it is in another national marine park, and not an island at all. In addition, there are a couple of other islets which offer probably the best chances to see Manta Rays and these are between The Similans and Richelieu Rock. Koh Bon and Koh Tachai may look too far away to bother visiting, but are in fact world-class diving sites.
Now, it may not concern most visiting divers whether they are in one national marine park or another. The fees to enter and dive at Mu Ko Similan National Marine Park and Mu Ko Surin National Marine Park are almost equal and not at all expensive. However, it is important for those who want to plan and book the ideal scuba Similan Islands diving trip to know where the best dive sites are located. There are large distances to cover between The Similan and Surin Islands, so that means time and expense. Anyone wanting specifically to visit one site or another needs to be aware of the distances and locations in order to make sure they get the most out of their diving trip. A quick look at the map on this page should clear up any confusion and allow those coming to dive in The Andaman Sea for the first time to better understand where everything is.
The Similan Islands is an archipelago of eight main islands and some rocks and pinnacles which breach the water’s surface. Most of the diving takes place around the middle of the chain, with the southernmost islands being closed to the public. There are almost two dozen fantastic diving sites, and several of the islands can be visited for beach activities or short treks. The Similan Islands are northwest of Phuket, and 60km. directly west of Khao Lak, in the province of Phang Nga. Most liveaboard boats and day trip speedboats and catamarans sail from Tab Lamu pier in Khao Lak, but a few sail from Phuket although it is quite a bit further.
To the north of The Similan Islands are three or four more great places to go scuba diving. In order, Koh Bon, Koh Tachai, Richelieu Rock and The Surin Islands all offer something special, yet different from each other. Distances from the northern point of this Similans to these other locations range between 22 and 80 kilometres.
Koh Bon is 22km. northeast from The Similan Islands’ North Point. It is highly-recommended and considered by many to be better than any of The Similan Islands’ diving sites. The island itself has nothing in the way of beaches or activities, but underwater there are two dive sites with deep and clear water. It is considered by most divers to be the best (most likely) place to see Manta Rays in Thailand. Khao Lak dive centres regularly visit Koh Bon for two-dive day trips.
25km. directly north of Koh Bon and 45km. from The Similans lies Koh Tachai. Like Koh Bon, it is a remote islet with excellent diving and likely opportunities to see Manta Rays. The island is larger than Koh Bon, and has a pristine beach which can be visited during surface intervals. It can be visited on its own on a day trip, combined with Koh Bon, or as part of a liveaboard cruise on the way to or from Richelieu Rock.
The Surin Islands are 80km. north of the Similans, and can be visited independently, with the nearest mainland pier in the northern part of Phang Nga province. The dive sites around the Surin Islands are excellent, but not substantially better than those at The Similans. The water is extremely clear, but not particularly deep. Snorkelling is extremely popular at The Surin Islands, and there are several endemic land species and birds which live there.
Richelieu Rock is the best dive site in Thailand. However, above the surface there is absolutely nothing, and it is not suitable for snorkelling. Richelieu Rock is between The Surin Islands and the mainland. At a distance of almost 90 kilometres from the nearest Similan Island, liveaboard cruise boats normally make the journey during the night. Being such a fantastic dive site, Richelieu Rock can be dived two or three times on the same day. It is a huge limestone pinnacle which almost reaches the surface and maximum diving depths are more than 40 metres. Whale Sharks are commonly spotted and even without them, the marine life is extremely healthy, diverse and colourful.
Now that you are more aware of where the best diving sites of Thailand are, all you need to do is choose a time and a boat then book your trip. June-October is unavailable, due to the parks being closed, and the New Year holidays are often fully-booked quite quickly. Manta Rays and Whale Sharks tend to be sighted more towards the end of the season than the beginning, but that is also when the sea conditions become more challenging.