The Similan Islands (Thai: หมู่เกาะสิมิลัน) is a group of islands in the Andaman Sea off the coast of, and part of, Phang Nga Province, southern Thailand. It is a national park, Mu Ko Similan, which was established in 1982 after a one year assessment by the forestry department.
The park is an archipelago consisting of 11 islands, occupying an area of approximately 140 km2 with a land area of about 26 km2. For convenience, the Thai Department of National Parks (DNP) has assigned numbers to the islands. From north to south, they are:
- Island 11: Ko Tachai
- Island 10: Ko Bon, AKA Ko Talu
- Island 9: Ko Ba-ngu, AKA Ko Bayu
- Island 8: Ko Similan
- Island 7: Ko Hin Pousar
- Island 6: Ko Payu, AKA Ko Pa Yu
- Island 5: Ko Ha
- Island 4: Ko Miang, AKA Ko Meang. Park HQ is here.
- Island 3: Ko Payan, AKA Ko Pa Yan
- Island 2: Ko Payang, AKA Ko Pa Yang
- Island 1: Ko Huyong, AKA Ko Hu Yong
Similan National Park is famous for its dive sites. It has typically two different kinds of diving. East side diving consists of gently sloping coral reefs with sandy patches with the occasional boulder in-between. The west side is known for its huge underwater granite boulders with numerous swim-throughs. Maybe the most famous east side dive site is East of Eden, off island number 7. Elephant Head Rock is arguably the most famous west side dive site with a maze of swim-throughs and the reputation for spin-cycle like currents running in every direction.
Elephant Head Rock was named by Horst Hinrichs from Germany in the mid-1970s, founder of one of the oldest dive shops in Phuket, Santana Diving. Other popular dive sites include North Point, Deep Six, Boulder City and the awesome pinnacles off Ko Bon and Ko Tachai.
The most important of all dive sites in the Similans, in reality part of Surin National Park, is Richelieu Rock, famous for its variety and abundance of marine life. Whale shark sightings are not uncommon here. However, since 1999, its once most beautiful dive site, Fantasy Reef, has been closed from all diving activities after its condition had significantly deteriorated. Park chiefs officially blame diving for the deterioration, while dive operators in the area claim that fishing boats, with or without permission, enter the national park during low season, when no dive operators are allowed in the national park. The national park also claims that the dive site suffered significant damage from the tsunami in 2004, and continues to keep the reef closed. Since only national park staff are allowed to dive Fantasy Reef, it has been impossible to confirm that statement.