Koh Similan or the Similan Islands is the number one site for scuba diving in Thailand and is in the top ten of the world dive sites. The 9 islands which compose the archipelago are located some 50km away from the shore of Khao Lak in the Andaman Sea. They are best accessed by Khao Lak or liveaboard boats.
The Similan Islands are open to the ocean, so a majority of the sites are recommended for advanced divers, but there are dive spots which are suitable for open water divers. In any case, you can gain your certifications there.
Koh Similan is a real playground for divers, with clear blue waters, spectacular coral reefs, an amazing marine life and several interesting wreck dives.
The best time to dive there is between November and May, but you can go all year round and enjoy some of the greatest dives in the world and even explore the Surin Islands.