Koh Bon

Koh Bon is one of the best places in Thailand to see manta rays, especially from April to May, though the last couple of years have seen Mantas almost year round. Koh Bon Island lies an hour or so north of the Similan Islands. It has a 33 metre wall on its south side, facing a small cove, with a stepped ridge pointing west and down to over 40m. It is at the edge of this ridge that divers are drawn as they peer into the blue looking for that first sight of a black and white fin that signals an approaching manta ray.
Manta rays are not the only reason that Thailand dive liveaboard cruises visit Koh Bon though. Leopard sharks are common at the ridge on the sandy flats below the wall, and white tip sharks can be seen roaming the depths off the edge of the reef. Soft corals the colours of turquoise, yellow and green dominate. Listen carefully and you'll hear the warning clicks of hundreds of nervous damselfish, and the coral crunching of hungry titan triggerfish, but don't neglect the wall itself which has plenty of critters to keep you interested including various types of moray eels.
To the west of Koh Bon Island lies Koh Bon Pinnacle. This Thailand diving site lies in deep water (18m - 40m) and is exposed, so consequently it is only possible to dive here in favourable conditions with experienced or advanced liveaboard divers. The west wall is steep, covered in small, yellow soft corals, and has a large cavern with a fish trap at its entrance. There is a smaller pinnacle lying to the north. Making your way back up the mountainous terrain, keep your eyes out for passing eagle rays, black tip sharks, and manta rays.
The small cove of Koh Bon provides good grounds for a night dive. The reef is made up of pore corals, with shrimpgobies peering out of the holes, and coral ledges. There are splendid decorator crabs, the intelligent red octopus, and red and white banded boxer shrimps.

Koh Tachai
Koh Tachai (Tachai Island) lies about halfway between the Surin and Similan Islands and is rated as one of the best sites for Thailand diving liveaboards as it's normally visited on the way to Richelieu Rock from the Similans. There are several dive sites around the island but the most famous is Koh Tachai Plateau which lies southeast of the island, about one kilometre offshore. The plateau is a submerged crowned reef of hard sheet corals, and scattered boulders. These boulders provide great swim-throughs and cut-through opportunities. They also provide refuge for tired scuba divers caught unawares by the sometimes hectic currents! This site is renowned for its currents and a dive briefing on any Thailand liveaboard scuba trip will include advice on where to find shelter. A dive here is not for beginners and not always easy but it is worthwhile because, as any diver knows, where there are currents there are big fish. Chief among these are manta rays who make regular appearances and effortlessly glide over the boulders. Other big visitors are whale sharks and nurse sharks. Leopard Sharks are common and hawksbill turtles are often seen. Other common fish you'll see here are blue-dash and yellow-backed fusiliers, red-tooth triggerfish, bigeye trevally and unicornfish.
The south side of Koh Tachai is the deeper side, and a logical place to start your dive. The north side features a huge abandoned fish cage which is useful as a navigational aid. At the edge of the coral crown is a cleaning station, popular with tiera batfish which always makes for a pleasant safety stop as you hang on the line at the end of the dive. Koh Tachai is often dived early morning by liveaboard but also makes a nice sunset dive.

Richelieu Rock
Richelieu Rock rates as one of the best places in the world to dive with whale sharks and is easily the best site in Thailand diving for this amazing activity. Encounters with the whale sharks, the largest fish in the ocean, are rare almost everywhere in the world. It's not the only Thailand dive destination where whale sharks are seen but Richelieu Rock certainly attracts more than its fair share. With nothing else for miles around, the whale sharks are attracted to the rock to feed on the rich planktonic blooms that occur here. A liveaboard charter is your best bet for diving here, as once they arrive, they tend to hang around for days, with an entourage of followers in tow, most notably cobias. Swimming with such a large animal, known to grow to fourteen metres in length, is a never to be forgotten experience for any diver. Sightings occur about 10% of the time. Some dive seasons see more visitors than others and generally February to April is the best time for a visit if your aim is to enjoy the exhilaration of swimming with these massive creatures onboard liveaboards in Thailand.
Richelieu Rock boasts great biodiversity too and is worth several dives, with or without whale sharks. It consists of one main, horse shoe shaped splintered rock pinnacle, with several other smaller rocks around its edges. The limestone rocks are covered with anemones, sea fans, barrel sponges and soft corals of all kinds. From tomato anemone fish, yellow boxfish, white-eyed moray eels and mantis shrimps to nurse sharks, manta rays one metre Malabar groupers and chevron barracuda, there's always plenty of life to grab your attention on this dive.
The problem for underwater photographers diving Richelieu Rock is which lens should you dive with. On the one hand there's the resident frog fish and seahorses that make such willing macro photo subjects. Mating cuttlefish and octopus are also common sights. Then, on the other hand, there's the chance of something really big swimming by and leaving you wishing that you'd selected your wide angle lens! Richelieu Rock can be a deep dive but there is also plenty to see at shallow depths all the way to the surface. When the currents are strong there are always places to find shelter.

Surin Islands
The dense and extensive reefs of the Surin Islands have the greatest hard coral diversity in Thailand. Though the soft corals and fish diversity are not as good as some of the other Andaman Sea destinations, you will find lots of turtles here and fish species that you won't see in the Similans, such as Napoleon wrasse, bumphead parrotfish, barramundi cod, yellow-mask angelfish and tomato anemonefish. Not many liveaboard dive cruises visit these islands. This is not because the diving in Surin is inferior to other Thai destinations, but rather due to the greater geographic remoteness and the short four day schedules of popular scuba safaris - not enough time to take in Similan and Surin. This means that when you do visit here, you'll find there's still a beautiful corner of Thailand that you can enjoy without sharing it with hordes of other tourists. Located 7 km south of the Burmese border and 68 km north of the Similan Islands, this island group was designated a national marine park in 1981 and is made up of two main islands - Surin Nua (North) and Surin Tai (South) - plus three smaller islets and two rocky outcrops. The islands are uninhabited except for the national park camp and a traditional Mokken sea gypsy village (the same group that roam the Burma Mergui Archipelago). The world famous dive site of Richelieu Rock lies 15 km further to the east.

Along the east coast of Koh Torinla a hard coral plateau breaks the water's surface at low tide. Large fields of staghorn corals and massive porites corals dominate the shallows. Cardinalfish, humpnose bigeye bream, twin-spot and five-lined snappers profilate. Just off the coast lies a 120 metre long rocky ridge that acts as a magnet for fish life. Pinnate batfish, blue-lined and pickhandle barracuda are common on the deeper east side that drops to 31 metres, and Spanish mackerel and grey reef sharks often pay fleeting visits. White tip reef sharks frequently rest on the surrounding sands or can be spotted cruising the ridge top at 7 to 25 metres.

To get back to the reef slope you'll need to pass over an expanse of sand, where eagle rays and shovelnose rays occasionally travel. This area hosts mantis shrimps and the endemic Andaman, or blue-spotted, jawfish. You may be lucky to sight this most colourful family member hovering above its rubble burrow. Else you may be even luckier to see it peering out of its burrow, replete with a full brood of eggs delicately balanced in its protective mouth.

At the South East Point of Surin Tai two parallel jumbles of boulders run out perpendicular from the shallow reef flat into deeper water, where strong currents can whip up and attract reef sharks. Shelter in the refuges provided by these rocks and spend some time examining the soft corals and fans for harlequin ghostpipefish and robust ghost pipefish. Black and blue ribbon eels and cowrie shells also inhabit the rubble floor and crevices here. Back on the reef slope you can capture your breath whilst ticking off Andaman rabbitfish, Indian sailfin tang and Andaman sweetlips (wite body with black dalmatain-like spots and yellow tail). The Surin area has some particularly attentive titan triggerfish, acting like over-protective parents guarding their unborn young - don't you just love 'em?

One of the major attractions of Surin is snorkelling. This is because in many places the reefs have grown right up to just one metre or so below the water's surface, bringing the marine life that much closer to the snorkeller. This is particularly so at Koh Torinla in the south and Koh Chi in the north. Here the reefs are very healthy and black tip reef sharks, conspicuous only by their absence from the Similan Islands, are regular visitors. This means Phuket liveaboard charters to Surin are ideal for non-divers and avid divers alike.

Many of Thailand's islands boast fantastic scenery and Koh Surin is no different. Indeed, many visitors claim that the topside beauty of Surin's verdant evergreen forests, laced with small beaches and mangroves, surpasses even that of the Similan Islands. If you get the opportunity to take a walk through the forests then watch out for crab-eating macaques, flying lemurs and flying foxes, as well as deer and squirrels. Bird watchers can enjoy sightings of hornbills, Nicobar pigeons, collared kingfishers, drongos and babblers, as well as birds of prey such as sea-eagles and kites. Turtles still follow an age-old ritual to come ashore here and lay their eggs. The hatchlings enter the Andaman Sea and swim as far as the Nicobar Islands and the east coast of the Malay Peninsula.