The islands are universally recognized as some of the best world-class diving. .The Similan Islands National Park lies some 100km or 4 hours from Phuket. The word "Similan" is derived from the Malaysian word " sembilan " which means "Nine" and there are nine granite islands.
The islands had never been inhabited. For many generations, the only human visitors were the so-called Sea Gypsies who came to fish on the teeming reefs. The Similan Islands were formed some 100-150 million years ago. There present formation is derived from cracked granite rock which has been sculpted from the winds and waves.
The Nine Islands in the similan group are: (running from North to South):
Koh Bangu (No.9), Koh Similan (No.8), Koh Pabu (No.7), Koh Payu (No.6), Koh Ha (No.5), Koh Miang (No.4), Koh Payan (No.3), Koh Payang (No.2) and Koh Huyong (No.1).
The Similans were designated as a National Park in 1982. The National Marine Park take great pride in the conservation of the islands and have closed islands No.1-3. Island No.1 is turtle inhabitation.
High season in this area officially begins in November, and ends in May, but the visibility varies all year round, from generally 20 metes to sometimes over 40 metes.
On the west side of the islands, the granite has been eroded into massive blocks. Diving here, you can explore swim-through, avoiding the huge sea fans, you may see a shy white-tip or black-tip shark, as they speed off into the blue. In good visibility, the granite boulders truly can seem like an underwater city. On the east side of the islands, you can drift through coral gardens and streams of fusiliers, watch dozens of feather worms pop closed as you pass, or observe fields of garden eels, swaying in the sand.
Of course, no trip to the Similans is complete without visiting the nearby Surin National Park. This is the site of the Richelieu Rock, world-famous for sightings of the magnificent, yet gentle, whale shark. Also, Ko Bon and Koh Tachai are top class dives and are the best places to see manta rays.
The reefs are home to a multitude of tropical fish of all sizes, shapes and colours, with frequent sightings of turtles, rays and sharks. ironwood and gum trees are among the larger trees, while jackfruit, rattan and langurs, squirrels, bats, lizards and a good variety of birds. But the most striking feature of these islands, at first glance, are the huge boulders that litter the western and southern shores on several of the islands.
But most of all the Similans has it all for divers from coral walls, big rocks, huge sea fans and barrel sponges, caves and swim-through's.