The Jewels of Thailand and the Andaman Sea

Season: Late October-May

Visibility: 15-35M/50-115ft

Water Temperature: 26-28C

Thailand is home to a diverse range of marine life (Image by Thailand Aggressor).

The tumbling granite rocks of the Similan Islands, the Surins and world famous Richelieu Rock offer experienced divers some truly thrilling experiences in the eastern Andaman Sea. Magnificent coral reef diving is enhanced by the possibility of Whale Shark and Manta Ray encounters during the spring months as these amazing giants of the sea migrate along the west coast of Thailand. The southern section of the Mergui Archipelago and the open ocean seamounts of the Burma Banks offer a fascinating and unusual underwater terrain – this is wilderness diving at its most exciting. There can be little doubt that liveaboard diving here offers one of the finest opportunities to view some of the ocean’s biggest fish!


The Similan Islands are located some 80-100 kilometres northwest of the popular holiday island of Phuket and are one of Thailand’s National Parks. Composed of nine granite islands, covered in dense jungle and fringed with beautiful sandy bays, the Similans offer some of the most varied dives for the experienced diver. Each island has its own name but everyone knows them simply by number. Many of the islands have gorgeous beaches with talcum powder-like sand. Diving off the Similans offers two completely different types of diving. The eastern sides of the islands are sheltered from the prevailing summer monsoon winds and feature dive sites with flourishing hard and soft corals studded with anemones. Here you can take a drift dive amongst colourful coral gardens, richly populated with brilliantly coloured reef fish. Dives on the exposed western side, which receives the full force of the southwesterly monsoon blowing from late May to September, are a different proposition with remarkably strong currents which swirl around the giant granite boulders, making diving more strenuous and navigation more important. The rewards for the adventurous diver include exciting swim-throughs and a superb variety of fish on show. Leopard Sharks and Blue-spotted Stingrays are often seen. Garden eels peep shyly from their homes and larger moray eels can be found lurking in their daytime hideouts. Soft corals cover every available ledge and boulder. Huge gorgonians fan out into the current and yellow tube sponges add their brilliance to the underwater scene. Jawfish, the elegant Ornate Ghost Pipefish, frogfish and Ribbon Eels are amongst some of the rarer creatures that your divemaster will be pleased to help you find. For those with an interest in marine biology it would be hard to find a more fascinating destination. At Elephant Head the underwater terrain is quite breathtaking. Huge boulders form daring swim-throughs with caverns, arches and grottoes to explore. Hard corals give way to soft corals at depth. Both the elegant Imperial and Emperor Angelfish can be found here, along with schools of Yellowtail Snappers and Yellowtail Fusiliers. Currents can be strong at East of Eden, but a moderate current will enable divers to search for the elusive Bowmouth Guitarfish or perhaps encounter a Leopard Shark. Another dive site which can sometimes be swept with current is the small collection of rocks which break the surface of the water at Sharkfin Reef. Swim through an opening in the rock to dive either side of this dive site. Some of the classic fish of tropical reefs can be observed here, including the elegant Moorish Idol, bannerfish, batfish and surgeonfish. Passing sharks and rays can also be observed from this area. Because there is a lack of mooring sites, or if the sea is too rough to hook on to one, several of these dive sites involve knowing how to make a ‘live-boat dive’ entries. This involves jumping into the water while the boat is still moving, although the engines are shut down!


Lying just a few kilometres from the Burmese border, the five Surin Islands are closely grouped, with the main island larger than any of the Similans and covered in verdant forest, with a few fruit trees and some deciduous trees bearing rich colonies of epiphytes. A small community of Chao Ley Sea Gypsies lives on the east coast. Well to the south of the Surins is the island of Koh Tachai, a famous dive site with some spectacular underwater scenery as well as superb marine life. At the island’s southern point, two large rock pinnacles project from the reef. Schools of batfish and barracudas circle the site, which is also popular with stingrays and many other fish. Huge sea fans make good use of the moderate or strong currents.

Listed as one of the world’s top locations for spotting Whale Sharks and Manta Rays, Richelieu Rock, covered in soft corals, acts like a magnet in attracting fish. Spotfin and Common Lionfish, Moorish Idols, Bearded Scorpionfish, Titan Triggerfish along with urchins, crabs and a variety of nudibranchs are found here. Being the only major source of food in this part of the underwater realm there is little wonder that this is a premier site for large pelagics with Rainbow Runners, Great Barracuda, jacks, tuna and trevallys often found hunting. This truly special dive site offers  opportunities to observe some of nature’s most prized and spectacular secrets: mating cuttlefish, swirls of schooling barracudas and, of course, the Whale Sharks and Manta Rays. More Whale Sharks are encountered at Richelieu Rock than any other location in Thailand and it is justifiably known as THE place to see Whale Sharks. Furthermore, one animal will often stay around for several hours enabling the diver to swim with this huge fish that must surely be every diver’s holy grail. A dive with a Whale Shark is incomparable. Such size, such elegance, such beauty is hard to describe, but the reality is so incredible that if you are lucky enough to be so favoured the memory will live with you forever!


This area of over a hundred islands and reefs has one feature that the Thai dive sites lack: good anchorages. The many deserted coves and bays are fringed with white sandy beaches and the crew of Ocean Rover reckon that there is a bay for every boat in any weather! Mostly uninhabited and rarely visited, these islands invite exploration. Black Rock is definitely a ‘high voltage’ dive. As the crew of Ocean Rover say, there must be many fabulous small creatures here, but it is difficult to concentrate on them when you are being buzzed by sharks, rays and schools of big jacks! Recent sightings include Bull, Grey Reef, White-tipped Reef and Silver-tipped Sharks. Rays, too, are well represented here with sightings of Manta Ray, Marbled Ray, Jenkins’ Ray and the rare Mangrove Ray. Schooling Mobula Rays and Spotted Eagle Rays are also on the list... and the crew say their explorations are only beginning! In the Burma Banks, which are so far offshore that only the bigger liveaboards can make the journey, the emphasis is also on shark encounters. With no coastline or islands in site, the banks have to be located by GPS. The four banks, Silvertip, Rainbow Reef, Roe and Big Banks, are swept by strong abrasive currents which have created gothic-like coral and rock formations with large plate and table corals, some up to 5 metres in diameter. Western Rocky island, located in open ocean fifty miles from the nearest shore, has a sloping reef on the northeast side and wall diving elsewhere. The sandy bottom, at about 30 metres, is dotted with boulders and coral heads. A large tunnel runs right through the length of the island and large Nurse Sharks sleep here along with scores of crayfish. On almost every dive sharks are seen. White-tipped Reef, Grey Reef, Black-tip Reef, Bull and Nurse are amongst the most commonly sighted species. Submerged reefs surrounding the island are covered with large fan corals and very colourful soft corals.


Hin Daeng and Hin Muang, in the Koh Lanta Marine National Park, are often considered ‘twin’ dive sites. The visibility is often a highly respectable 20 metres plus, marine life is prolific and few boats venture this far from land (it would take over 5 hours to reach this area by day boat), so the coral and marine life is generally amongst that best that Thailand can offer. Add to this good opportunities for meeting Manta Rays, Whale Sharks, a variety of pelagic fish and some oceanic sharks and you will see why Ocean Rover visits this exciting area. Hin Muang or Purple Rock consists of several submerged pinnacles, with the shallowest lying around 8 metres below the surface and the deepest drop off being over 70 metres. The offshore location means that large pelagics frequently visit this area. Sightings include some minibus-sized tunas and some huge barracudas. Keep a look out for Whale Sharks as well as Manta Rays. The pinnacles are covered in purple coral which literally drips from the pinnacle walls. Hin Daeng or Red Rock has equally stunning scenery, but here the reef walls are draped in red soft coral. Silversides can be seen flashing and shape-shifting like silver ghosts, but the real attraction, like Hin Muang, is the ready supply of visiting pelagics. Grey Reef Sharks are commonly seen, while Manta Rays and Whale Sharks are also visitors to the area. Check out a cave at around 30 metres on the south west wall for some large Nurse Sharks.

Currents in all the Thailand and Burma dive sites can be strong, with surface conditions frequently choppy. This is a destination for good sailors and more experienced divers.


Divequest offers a variety of land extensions into fascinating countries  that neighbour Thailand including Myanmar and Cambodia.  

Why not combine your diving trip with a journey around the temples of Angkor Wat or Bagan?  

We are also a leading operator of nature tours in the South East Asia region.  Talk to us about some opportunities.


A watchful octopus in Thailand (Image - Alex Mustard)

Thailand offers an occasional chance to dive with Leopard Sharks (Image - Mark Strickland)

There are some wonderful reef walls and drop offs in Thailand and Burma (Myanmar) (Image - Mark Strickland)

On dives at Richelieu it is hard to know which lens to take - a macro or a wide angle (Image - Aggressor Fleet)

Whale Sharks are a seasonal delight (Image - Mark Strickland)

Explore intact gorgonian corals on the reef walls (Image - Mark Strickland)

The reefs of Thailand can be richly abundant (Image - Aggressor Fleet)

Glow in the dark squid (Image - Aggressor Fleet)

Schooling batfish are always a highlight (Image - Aggressor Fleet)

Explore coral caves and grottoes (Image - Aggressor Fleet)

Get up close and personal with a Parrotfish (Image - Aggressor Fleet)

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