8 Best Dive Sites in Thailand by Coast and Season

Featured image: Weldon Kennedy from London, UK, CC BY 2.0, via Wikimedia Commons.

Quick answer: the best dive sites in Thailand at a glance

Pick the Andaman Sea for manta and whale shark sites. Pick the Gulf of Thailand for easy bases and cheaper courses. Andaman diving runs best from November to late April, while Gulf diving peaks from March to September. Our table matches each site to a coast, base, access type and level.

8 best dive sites in Thailand, ranked

Prices and hours checked November 2026. We rank by marine life first, then by how easy each site is to reach. Depths are typical ranges, and operators sometimes quote different numbers for the same site.

1. Richelieu Rock

Richelieu Rock is our top pick because one horseshoe-shaped rock pulls in most of what the Andaman holds. It sits near the Burmese border, well away from larger land masses, so it is fully exposed. That exposure limits bottom time, and boats usually fit in two dives here.

Look for pairs of cuttlefish around the coral outcrops, plus schools of pelagics and a chance of mantas or whale sharks. Operators cite February to May as the strongest window for big animals in this part of the Andaman. Pass on it if you want a day-trip itinerary, because this site is liveaboard territory.

2. Hin Daeng and Hin Muang

Hin Daeng (Red Rock) and Hin Muang (Purple Rock) are the southern Andaman highlights. Both are submerged rocky ridges that drop into deep water, with soft corals in the shallower parts. Hin Muang takes its name from swathes of purple soft coral.

Mantas, whale sharks and leopard sharks are all cited here, and schooling pelagics gather around the rock. Some divers report these southern sites are less crowded than the Similans, especially with early and late dives that miss the Phi Phi and Koh Lanta day boats. Give it a miss if you need a sheltered, easy first dive.

3. Koh Bon and Koh Tachai

Koh Bon is a horseshoe-shaped island with a hole through it, and it is the place to see manta rays in Thailand. Cleaning stations sit along the point and the outer hard coral reef. Koh Bon Pinnacle lies roughly 100 m offshore, with its top 11–14 m down, so your safety stop is likely in open blue water.

Koh Tachai Pinnacle, nicknamed twin peaks, has two submerged peaks joined by a shallow rock expanse. Trevally hunt between the peaks when the current runs, and mantas and whale sharks are both reported. Not for divers who are uneasy with strong current.

4. Chumphon Pinnacle

Chumphon Pinnacle is a cluster of rocky outcrops about 45 minutes by boat from Koh Tao. Three moorings sit over a top roughly 10 m (33 ft) down, and the sand floor reaches about 34 m (110 ft). Operator guides quote depth ranges such as 12–35 m, so expect small differences between boats. Fields of anemones cover the top, and batfish, barracuda and snapper cruise past.

Bull sharks patrol the base, and whale sharks have been seen here. Many divers report heavy boat traffic, so ask your center for the earliest departure. Avoid it if solitude matters more than sightings.

5. Sail Rock

Sail Rock is the Gulf's other headline pinnacle and competes with Chumphon for best Gulf site. Boats take about 1.5 hours from Koh Tao, and the run is much shorter from Koh Samui. Maximum depth is about 40 m (131 ft). A chimney lets you descend inside the rock and exit at different depths.

Barracuda form large schools, and a whale shark turns up on lucky days. Most trips offer 2–3 dives with breakfast and lunch, and cost a little more than a normal boat day because of fuel. Trips are usually announced a few days ahead, and rough water makes the long crossing a poor fit for anyone prone to seasickness.

6. Koh Bida Nok and Koh Bida Nai

These two limestone outcrops lie just outside Koh Phi Phi and are regular day trips from Phuket. Bida Nok is probably the best Phi Phi site, with soft corals, sea fans and hard corals around the base of the cliffs. Leopard sharks, reef sharks, turtles and barracuda schools show up here.

Bida Nai is the smaller sister islet with similar life, a large swim-through and a coral-covered wall. Water gets rougher and the bottom drops deeper at Bida Nai. Skip them if mantas are your goal; the Andaman pinnacles do that better.

7. Similan boulder sites: Anita's Reef, Shark Fin Reef and Elephant Head

Granite boulders, gorgonian sea fans and white sand give the Similans a different look from the pinnacles. Anita's Reef and East of Eden have coral bommies covered in hard and soft corals, best with a little current. Shark Fin Reef and Boulder City are southern sites where schooling pelagics, mantas and leopard sharks can appear.

Elephant Head Pinnacle has an unmarked top about 11 m down, so boats need a depth finder to locate it. Watch your no-decompression limit there, as the dive is not for beginners. Some operators run Similan day trips by speedboat from Khao Lak, but most visitors come by liveaboard from November to the end of April.

8. HTMS Sattakut and HTMS Suphairin

Koh Tao's wrecks give the Gulf a deeper, structured alternative to its pinnacles. HTMS Sattakut is an old naval vessel sunk on purpose, lying at 20–30 m. With a 20 m minimum depth, Sattakut needs at least Advanced certification, and Hin Pee Wee (8–28 m) sits beside it. HTMS Suphairin is a Royal Thai Navy vessel reportedly sunk in 2023, also at 20–30 m.

Penetration requires wreck certification, though the guns and wheelhouse reward a look from outside. Visibility at Sattakut is not always good, so keep expectations modest. See our guide to Thai wreck dives for more.

Best time to dive in Thailand, by coast

On the Andaman side, the best season runs from November to late April or early May. Similan liveaboards follow November to the end of April. Divers report that Similan and Surin waters close from May to October, so check dates with the Thai National Parks Department. When the parks close, several boats switch to southern itineraries. In the Gulf, March to September is the usual window, with June and July often giving the best visibility. Many divers report that June crossings to Koh Tao can turn rough, so earlier or later weeks suit fussy divers. October to February brings more rain to the Gulf. Our Andaman coast guides cover the west side month by month. For the east, see our Gulf-side dive options.

Best dive sites by marine life

Mantas and whale sharks are most often reported at Koh Bon, Koh Tachai, Richelieu Rock, Hin Daeng and Hin Muang. Chumphon Pinnacle is the Gulf's whale shark site, and bull sharks patrol its base. Leopard sharks favor the Phi Phi and Phuket sites, including Koh Bida Nok. Turtles appear on both coasts, more regularly on the Andaman side. Cuttlefish pairs are Richelieu Rock's signature. For macro, White Rock, Green Rock and Red Rock at Koh Tao offer shrimp and pipefish.

How to choose: certification, crowds and budget

Certification narrows the list fast. Sattakut needs Advanced because its minimum depth is 20 m. Elephant Head Pinnacle is not for beginners. New divers do well at Twins (5–18 m) and Japanese Gardens (1–14 m) off Koh Tao. For crowds, forum divers report heavy boat traffic at Chumphon Pinnacle and the Similans. Their workaround is early or late dives, or less-visited sites such as the southern Andaman. Opinions also split on whether Thai diving has declined. Forum divers say quality dropped and costs rose. Operator guides describe Similan sites reopening and recovering. We would not pick a side without current dive reports from your chosen operator.

Cost and booking trade-offs

Koh Tao is the cheapest base and the most course-heavy. Dive prices there are generally set across shops, so choose an instructor rather than hunting discounts. Phuket and Khao Lak day trips sit in the middle. Liveaboards cost the most but reach Richelieu Rock and Koh Tachai. Short trips start at 3 days, and 4–6 day trips cover the whole region. Park entry is separate, and one older guide says foreigners pay a multiple of local rates. Confirm current fees with the park authority. For a fuller breakdown, read what diving costs in Thailand.

Getting there and where to base yourself

For Koh Tao, fly to Chumphon, Koh Samui or Surat Thani, then take a ferry such as Lomprayah. All boats arrive at Mae Haad pier. Samui is the shorter run to Sail Rock. Most Andaman liveaboards leave from Tap Lamu Pier, about an hour's drive north of Phuket airport. Others depart Chalong Harbour in Phuket. Khao Lak works well before or after a trip. Compare dive resort options for stay-and-dive packages. If you plan several nights afloat, see planning a multi-day dive trip.

Mistakes to avoid

Do not expect Similan-level life at a beginner site like Twins. Do not assume every site is open, since park closures run May to October. Do not forget park fees. One diver also reports that June in Koh Tao can be windy, with rougher crossings and weaker visibility. Finally, do not book the deepest wrecks or pinnacles without the right certification.

Southwest Pinnacle: Koh Tao’s mid-depth alternative

Southwest Pinnacle is a useful Koh Tao choice when Chumphon Pinnacle is busy or conditions make a different route more appealing. The site ranges from roughly 5 m to 30 m, so dive centers can plan a shallower circuit or a deeper profile around the same pinnacle. Its Gulf location also makes it easy to combine with a Koh Tao-based stay.

Plan this as a site for certified divers who are comfortable managing depth and changing conditions. The 5 m upper area can suit a conservative finish, while the 30 m lower sections need more careful gas and no-decompression planning. Ask your operator which mooring and route they expect to use that day. Conditions, visibility and current can change the appropriate profile.

Southwest Pinnacle works best as part of a flexible Koh Tao dive schedule. Keep Chumphon Pinnacle or nearby shallower sites as alternatives, rather than booking one specific pinnacle too far ahead. This approach is especially useful when boat traffic or sea state affects the day’s route.