Located 70 kilometers off the cost of Phang Nga, the Similan Islands are, according to many, the best preserved marine ecosystem in Thailand, with accordingly the best scuba diving to be had in the region. The Similans are a chain of nine rocky islands running in a north - south line. The Similans National Park, created in 1982, also includes two additional islands, Koh Bon and Koh Tachai.
The Similans are very popular with divers, and you'll find a complete on-line guide to Similans dive sites at SEA Undersea, but you can visit the islands even if you're not a diver. You can enjoy the relative solitude of the white sandy beaches, camp out, and go snorkeling.
There is no regular boat service to the islands. Divers generally reach there on live-aboard cruises. You can also book day trips at travel agencies around Khao Lak or Phuket.