Similan Islands
Thailand · Andaman Sea
A chain of nine granite islands in the Andaman Sea, the Similans deliver clear water, boulder strewn topography, and reliable big fish action at the northern sites (Richelieu Rock, Koh Bon, Koh Tachai). Most diving is by liveaboard from Khao Lak.
How this reef is doing
ⓘ How we measure thisReef state
Granitic boulders and reef. Cover thinned by recurrent bleaching; trips still go for the topography and pelagics.
Coral cover
Fish life
Heat
Warmer than usual right now, but not hot enough to bleach.
Fishing
Quiet water, and the protection is actively patrolled.
Sources · MERMAID and partner coral surveys · NOAA Coral Reef Watch · Global Fishing Watch and reef gravity
What you will see
12 species across the dive sites here
Schooling glassfish
Seen 2 months ago
at East of Eden
Least concern
Leopard shark
Seen 2 months ago
at Elephant Head Rock
Whitetip reef shark
Seen 3 months ago
at East of Eden
Vulnerable
Common Water Monitor
Seen 3 months ago
at Elephant Head Rock
Least concern
Redlip Parrotfish
Seen 3 months ago
at Elephant Head Rock
Least concern
Blue Dragon
Seen 3 months ago
at Elephant Head Rock
Moorish Idol
Seen 3 months ago
at East of Eden
Least concern
Hawksbill turtle
Seen 4 months ago
at East of Eden
Critically endangered
Tigertail seahorse
Seen Apr 2025
at East of Eden
Endangered
Napoleon wrasse
Seen year round
at Elephant Head Rock
Endangered
Octopus
Seen year round
at Elephant Head Rock
Least concern
Schooling fusilier
Seen year round
at Elephant Head Rock
Least concern
Dive sites
What divers say
Richelieu Rock in March with a whale shark cruising past purple soft coral — peak Thailand diving.
Good to know
Park closure
Closed approximately May 16 – October 15. Confirm dates yearly.