At Sail Rock, a granite pinnacle rises from 40 metres of water halfway between Koh Phangan and Koh Tao, and the barracuda tend to arrive before the divers have finished their descent. Koh Samui itself has few dive sites of note. What it has is position: the island is the launching point for the best diving in the lower Gulf of Thailand, and a cluster of long-established dive centres that make the trip every week.
This guide covers the main dive sites within a day's reach, the centres with the longest track records, how certification works, and the months that give the best visibility. Samui Beach Club does not sell or book dives. The centres below are listed because their affiliation is confirmed with PADI or SSI, they hold a current tour business licence from the Department of Tourism, and their reputation with divers is strong.
The Dive Sites
Sail Rock (Hin Bai): the headline site. The pinnacle drops to around 40 metres, and a vertical chimney lets divers swim through the rock down to 18 metres. Barracuda, batfish, and trevally are regular sightings, and whale sharks are seen here fairly often. The trip takes between 45 and 90 minutes each way, depending on the boat.
Koh Tao: a full day from Samui, with reef and pinnacle sites all around the island. Chumphon Pinnacle, north of Koh Tao, is one of the deeper and more dramatic dives on offer.
Ang Thong National Marine Park: mostly shallow, around 10 metres, and often murky, but sheltered and scenic. It suits snorkellers and new divers more than those chasing visibility. The park closes every year from 1 November to 15 December.
Koh Tan and Koh Madsum: two small islands off the south coast, with shallow coral and calm water for snorkelling.
Discovery Divers
Discovery Divers is a PADI 5 Star IDC centre and has been a PADI member since 1999. It is based at the Amari resort in north Chaweng and sails from its own pier.
The centre offers try dives for complete beginners, PADI courses up to Divemaster, and daily boat trips to Sail Rock and Koh Tao. A long run of positive reviews from visiting divers backs up its reputation.
- PADI 5 Star IDC, a PADI member since 1999
- North Chaweng, at the Amari resort; own pier
- Try dives, courses to Divemaster, daily Sail Rock and Koh Tao trips
Discovery Divers
PADI diving courses and Gulf of Thailand dive trips from Chaweng Beach
Member Diving
Member Diving is a Swiss-run centre in Bophut, founded in 2013 and registered with SSI. It is a good choice for divers who prefer SSI certification or a smaller, more personal operation.
Courses cover introductory dives, Open Water, Advanced, and Nitrox. Trips sail by catamaran to Sail Rock, Koh Tao, and Ang Thong, and there are snorkelling tours and private charters as well.
- SSI dive centre, Swiss-run since 2013
- Bophut, on the north coast
- Catamaran trips to Sail Rock, Koh Tao, and Ang Thong
Member Diving
Scuba diving, courses and snorkelling trips from Bophut Beach
100 Degrees East
100 Degrees East has worked from Bangrak for more than 20 years. It is a PADI 5 Star Dive Resort, but its reputation rests just as much on small-group snorkelling trips, which cap numbers at 12 and include national park fees.
Ang Thong and Koh Tao are the main snorkelling destinations, and diving and private charters can be arranged alongside them. For a group where some dive and some snorkel, it is a practical option.
- PADI 5 Star Dive Resort, more than 20 years in Bangrak
- Small-group snorkelling to Ang Thong and Koh Tao
- Diving and private charters
100 Degrees East
Small-group snorkelling, diving and island trips by speedboat from Koh Samui
Getting Certified
PADI dominates on Samui, and SSI is also represented. Both are recognised worldwide, and either certificate is accepted at dive centres abroad. The usual entry point is a try dive, which needs no previous experience, followed by the Open Water course, which typically takes three to four days.
A centre's affiliation can be checked on the agency's own dive centre locator, on padi.com or divessi.com. It is worth doing before booking a course, since some smaller operators advertise courses they are not registered to teach.
Equipment
Courses and dive trips usually include equipment hire, though it is worth confirming when booking. Divers who would rather bring their own mask or computer, or need a replacement part, can visit Aquamaster, an established diving equipment supplier with a shop in Bophut.
Aquamaster Samui
Scuba, snorkelling and swimming equipment for island adventures
When to Dive
Visibility is usually at its best in March and April. April and May are the months most associated with whale sharks at Sail Rock and the pinnacles further north. June to September is a reliable period too.
The northeast monsoon makes November and December the hardest months. Seas are rougher, visibility drops, and some trips are cancelled. Ang Thong is closed altogether from 1 November to 15 December. A booking with some flexibility built in is sensible at any time of year.
Marine national parks ban sunscreens containing oxybenzone, octinoxate, 4-methylbenzylidene camphor, and butylparaben, with heavy fines for visitors who ignore the rule.
Samui is a gateway rather than a reef. The diving happens an hour or so out, on granite that rises from deep water, and the island's longest-running centres have spent decades learning when the conditions line up. The rest depends on the barracuda.
