Koh Dok Mai: Only 1 hour away from Phuket you can dive at this limestone Island.
The sides of the island are sheer walls rising up in the sky. The same thing can be found below the surface: straight walls dropping down to the bottom. On the walls you find lots of clams and corals like Whip corals, huge Gorgonian sea fans and a great variety of soft corals.
While facing the wall, look back sometimes to see Barracudas and other pelagics in the blue.
But what this site is the most popular for is macro. The walls house an enormous diversity of shrimps and nudibranch. More rare organisms like Ornate Ghostpipe fish and Frog fish can be found here as well.