The Similan archipelago consists of nine small granite islands located 92 km. (56 n. miles) northwest of Phuket island,  is a Marine National Park under the care of the Royal Forestry Department. 

The Similans is claimed to be one of Asia's top dive destinations, with an underwater terrain highlighted by thriving reefs, abundant soft corals and the tremendous diversity of marine life. 

The dive sites:- Maps

No. 1 - Koh Huyong: Around this island, are dive sites with depths averaging between 5 m. to 18 m. The sea-scape comprises of coral gardens teeming with a large variety of marine life, dominated by reef fishes. On the deeper eastern section, there are chances to catch a glimpse large underwater creatures like Manta Rays, large schools of Great Barracuda and  Whale Sharks.

No. 3 - Koh Payun: Around this island, are dive sites with depths averaging between 16 m. to 20 m. Featuring sloping reef, sheer drop offs, enormous submerged granite boulders. It offers a diverse range of marine life like the schools of batfish, surgeonfish, Moorish idols, banner fish, lionfish, blue spotted groupers, red coral trout and even barracudas.

No. 4 - Koh Miang: This island is the only  inhibited island in the Similans and around this island, are dives sites with depths averaging between 18 m. to 30 m. This offers deep dive and its best features being below 25m consisting of large towering rocks with alleyways, large granite boulders offering large sea fans, barrel sponges with the presence of reef fish, lionfish, bearded scorpion fish, large angelfish, tuna, barracuda, trevally and also leopard sharks. 

No. 5 & No. 6 islands: This two islands offers similar dive sites environment similar to No. 4 - Koh Miang, with the exception that here, it provides for adventurous drift diving. 

No. 7 - Koh Payu: Around this island, are dive sites with depths averaging between 18 m. to 23 m. The dive sites off Koh Payu, is where schools of snappers, fusiliers, turtles and leopard sharks can be found.

No. 8 - Koh Similans: Around this island, are dive sites and with depths averaging between 8 m. to 25 m. The dive sites off here offers one of the most colorful underwater sights of marine flora and fauna collection. 

No. 9 - Koh Bangu: Around the north-western tip of this island offers a depth of between 8 m. to 15 m of adventure diving with swim through amongst the rock formations. The enormous whale shark can  occasionally be seen swimming close to the underwater drop offs.

Bon Island

Bon Island located about 46 km. (25 n.miles) northeast of the Similans islands is a good site for manta rays and sometimes whale sharks. This is a good site for large pelagic. Huge sponges can also be found in depths of 30-40 m.

Tachai Island

Tachai Island located about 40 km. (22 n.miles) south of Surin islands, provides 3 multi level reefs at this site to venture in. The average depth is between 12 m. to 24 m. Soft and hard corals, sea fans, sea anemones and a variety of coral fishes can be found here.