Diving & snorkelling

The Andaman's best sites are liveaboard territory: the Similans and Koh Bon are three to five hours offshore. Day trips from Phuket and Krabi reach Koh Haa and the King Cruiser, which are good but not the same.

If you are not certified, a discover-scuba day is a sensible first step; if you are, tell us your logbook level and we will match the boat rather than the price.

The Andaman is the better diving and the Gulf is the better place to learn. The Similans and Richelieu Rock have the coral, the visibility and the big animals — whale sharks, manta rays, leopard sharks — but the crossings are long and the sites are deeper. Koh Tao certifies more divers than anywhere else in the world, which means cheap courses, warm water and a lot of other beginners.

The seasonal split is absolute. The Andaman runs November to April and the Similan park closes entirely from mid-May to mid-October. The Gulf runs the opposite way, with the best visibility on Koh Tao from March to September. There is no month in which both coasts are at their best, which is why serious divers plan two trips.

Snorkelling is a different calculation. The best snorkelling from shore in Thailand is at Koh Tao (Shark Bay, Aow Leuk), Koh Ma off Koh Phangan, and the Similans on a day boat. Reef quality has declined everywhere since 2010 through bleaching, so manage expectations — this is not the Red Sea.