Koh Bon and Koh Tachai are two remote islands which sit alone and between The Similan Islands chain and the Surin Islands. Koh Bon is nearer to The Similans, and Koh Tachai, a little further north, is nearer to Koh Surin. While they both offer excellent diving, and arguably the best chances of Manta Ray sightings, they share both similarities and differences. Both islands have healthy corals which support lots of fish invertebrates and even marine reptiles. The sea conditions are also similar, regarding depths, visibility and currents. In addition, they are ideal for speedboat day trips from Khao Lak diving centres. They aren't as far as Surin's dive sites, yet offer something different from The Similans' nine main islands. Koh Bon differs from Koh Tachai in that it has no beach. While it has more diving space underwater and the famous wall, there is nowhere for non-diving members of the group and those on their surface interval to hang out. Koh Tachai has this wonderful, pristine beach along its eastern coastline.