The Similans The Similans all well know group of islands in the Andamand sea and are are best done on a live abroad so you can sample different dive sites and hopefully get to see Mantas, trips generally run only from Nov – April. Famous dive sites there are – Elephant Head Rock, East of Eden North Point, Deep Six, Boulder City and the awesome pinnacles off Koh Bon and Koh Tachai. I went on a liveabord there in 2009 with KhaoLak Scuba Adventures a good outfit, friendly, helpful, fun and passionate about showing you marine life. Koh Tao I did my Recuse, EFR and Dive master Course on Koh Tao with Buddha View as this is a cheap place to get certified. The dive sites are ok and diverse macro life can be found but you’ll need to get a good guide. Koh Tao holds a special memories for me not only because I did my DM there, made loads of diving friends there but also it was where I saw my first ever Whale Shark. I still remember the moment vividly as the sight of this giant fish cursing silently and gracefully though the water. It takes your breath away. Good Dives sites around Koh Tao – Chumpoun, Twins, Green Rock and sail Rock (more towards KPG / Samui)
Other places i have dived in Thailand – Koh Chang, much the same as Koh Tao, not amazing marine life but a good dive all the same.