Koh Lanta

Koh Lanta, in Krabi province on the Andaman coast, is a laid-back island base for some of Thailand's best southern dive sites. Hin Daeng and Hin Muang, two remote pinnacles covered in red and purple soft coral, are known for manta rays, whale sharks and big schools of fish, while Koh Haa's lagoon, caverns and "chimney" suit divers of all levels. The season runs roughly from October to April, when the Andaman Sea is calm; many dive centres close or scale back during the summer monsoon. Koh Lanta's dive operators are known for small groups and comfortable day boats.