Koh Tao

Koh Tao — Turtle Island — is one of the world's great diving destinations and one of Southeast Asia's most charming small islands. At just 21 km², it's tiny enough to circumnavigate on a motorbike in 30 minutes, but the underwater world surrounding it is vast and richly populated: whale sharks (seasonal), leopard sharks, reef sharks, sea turtles, barracuda, batfish, and some of the Gulf of Thailand's healthiest coral reefs. The island has earned global recognition as the place to learn scuba diving — PADI Open Water courses cost around 9,000–11,000 THB (compared to double that in Australia or Europe) and take 3–4 days, including pool training and four open-water dives.

The island's above-water character has evolved from its original fishing-village simplicity into a comfortable backpacker-and-diver ecosystem — there are now over 60 dive schools, plus a growing range of upscale resorts, good restaurants, sunset bars on rocky headlands, and beachside cocktail shacks. Sairee Beach, the island's longest and most developed, has the full range of dive operations and accommodation. Mae Had, on the northwest, is where the ferry pier is located and has good cheap accommodation. The east and south coasts (Chalok Ban Kao, Tanote Bay, Ao Leuk) are quieter and largely undeveloped beyond a few resorts.

One of Koh Tao's most distinctive assets is its diving topography. The sites range from gentle, shallow coral gardens at 5–12 m suitable for beginners to advanced sites like Chumphon Pinnacle (40 m, regular whale shark encounters) and Southwest Pinnacle (30 m, strong current, manta rays) that challenge experienced divers. Sail Rock, equidistant between Koh Tao and Koh Phangan, is a submerged seamount with a dramatic chimney passage through the rock — considered the best single dive site in the Gulf. Night dives from Koh Tao encounter giant morays, sleeping reef sharks, and phosphorescent plankton.