Diving in Thailand

The Similan Islands are Thailand’s premier dive area: a chain of granite islands about 60 km off Khao Lak, with smooth boulders stacked into swim-throughs and arches on the west sides and gentle coral slopes on the east. Elephant Head Rock is the classic boulder dive, East of Eden the classic reef, and Ko Bon and Ko Tachai, the two outlying islands added to the park, are the best spots for manta rays. Visibility often reaches 20 to 30 m. The islands have powder-white beaches too, but overnight stays on land have been restricted in recent seasons, so divers come either on speedboat day trips from Thap Lamu pier (about 1.5 hours each way) or on liveaboards, which reach the remote sites at dawn before the day boats arrive.

Richelieu Rock, a horseshoe-shaped pinnacle that barely breaks the surface at low tide, sits further north in Mu Ko Surin National Park and is regularly ranked among the best dive sites in the world. It is Thailand’s most reliable place for whale sharks, mainly from February to April, and the rock itself is covered in soft coral, anemones and tiny subjects: seahorses, harlequin ghost pipefish and frogfish, with barracuda and trevally schooling off the edges. Because it is far offshore, nearly everyone reaches it on a liveaboard of three nights or more.

Phuket has the most dive shops in the country and runs day trips all year, mostly from Chalong pier. The favourites lie east towards Krabi: Shark Point (Hin Musang), a protected rock where leopard sharks rest on the sand among soft corals, moray eels and turtles; Anemone Reef next to it; and the King Cruiser, a car ferry that sank in 1997 and is now a coral-covered wreck at about 30 m. Ko Dok Mai, a sheer limestone island between Phuket and Phi Phi, is a wall dive with small caves, moray eels, sea snakes and nudibranchs, sheltered enough to dive on most days and popular at night. South of Phuket, Ko Racha Yai has calm bays used for training.

The Phi Phi Islands are easy to reach from Phuket, Krabi and Ao Nang, with most sites around Phi Phi Le and the Bida islets, Bida Nok and Bida Nai. Visibility is usually good, blacktip reef sharks and leopard sharks are seen often, and the walls are covered in sea fans. The islands draw huge day-trip crowds, so dive from a shop on Ko Phi Phi Don or a private longtail and time your dives before the speedboats arrive.

Ko Lanta is a relaxed base with a quieter scene than Phi Phi. Day boats run to Ko Haa, five small islands with a cavern called the Cathedral and easy reef dives, and to the pinnacles of Hin Daeng and Hin Muang, Thailand’s most exciting advanced dives. Red Rock and Purple Rock take their names from the soft corals that cloak them; Hin Muang has the tallest wall in the country, dropping to about 60 m. Manta rays and whale sharks pass in season, mostly from February to April, and grey reef sharks patrol the deep edges. Currents are strong, so these suit divers with experience and an Advanced certificate.

On the way back, boats often stop at Ko Rok for snorkelling or at Ko Muk, where you swim through an 80 m dark tunnel into the hidden lagoon of the Emerald Cave.

Ko Tao is one of the busiest places in the world to learn. Its sheltered bays are shallow, warm and calm for much of the year, there are dozens of schools along Sairee and Chalok Ban Kao, and courses are cheap because competition is fierce. Most beginners do the four-day Open Water and stay on for the Advanced. Experienced divers head for Chumphon Pinnacle, a granite pinnacle off the northwest coast with huge schools of batfish and trevally, occasional bull sharks and whale sharks in season. Twins and the Japanese Gardens at Ko Nang Yuan are easy reef dives.

Ko Chang in Trat, near the Cambodian border, has easy, uncrowded diving in the islands of Mu Ko Chang National Park to the south, around Ko Rang, Ko Wai and Ko Mak. The waters were the scene of the 1941 Battle of Ko Chang between the Thai and French navies, and today the main wreck is HTMS Chang, a 100 m former navy ship sunk on purpose in 2012 as an artificial reef. Sites are shallow and gentle, which makes the area good for fresh certifications. The season runs from about November to May.

The Andaman coast is best from November to April, when seas are flat and visibility peaks; the Similan and Surin parks close completely from mid-May to mid-October. Phuket shops keep diving a few sheltered sites through the wet season, but many days are rough. February to April is prime time for mantas and whale sharks on the Andaman side.

The Gulf runs to a different calendar. Ko Tao is good from March to September, at its best from about April to August, and diveable most of the year; only the northeast monsoon, roughly late October to December, brings choppy water and lower visibility. If you can only come in July or August, Ko Tao is the answer. Our best time to visit Thailand page has the weather month by month.

Liveaboards for the Similans and Richelieu Rock leave from Khao Lak and Phuket and fill early for February to April, so book a month or more ahead. Day trips and courses can be booked on arrival. Pick a shop affiliated with PADI or SSI, ask about group sizes (four divers per guide is good), and check that the boat carries oxygen. Marine park fees are usually paid in cash on the boat and are not always included in the trip price.

Make sure your travel insurance covers scuba to the depth you dive, or take dedicated dive cover such as DAN. Phuket, Ko Samui and Ko Tao have recompression chambers. Do not fly within 18 to 24 hours of your last dive, and be honest on the medical form about asthma or heart problems. The deep pinnacles have strong currents: carry a surface marker buoy and stay with your guide.