Richelieu Rock is 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. Here divers will encounter the largest fish in the ocean which are rare almost everywhere in the world. With nothing else for miles around, the whale sharks are attracted to the rock to feed on the rich plank tonic blooms that occur here.

• Dive Type: Boat Dive
• Diver Level: Novice Diver - 20 + Dives
• Max Depth: 40m

Koh Tachai is located in Tachai Island and lies about halfway between the Surin and Similan Islands and is rated as one of the best sites for Thailand scuba 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.

• Dive Type: Boat Dive
• Diver Level: Advanced Open Water Diver
• Max Depth: 35m

This dive site is one of the best places in Thailand to see manta rays, especially from April to May.
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 edge pointing west and down to over 40m.

Here divers will have the opportunity to see leopard sharks, white tip sharks; soft corals the colours of turquoise, yellow and green dominate. If you listen carefully you'll hear the warning clicks of hundreds of nervous damselfish, and the coral crunching of hungry titan triggerfish.

• Dive Type: Boat Dive
• Diver Level: Novice Diver - 20 + Dives
• Max Depth: 40m

Boulder city is a submerged site about one kilometre off the east coast of island number 3 and about 400 m south east of Shark Fin Reef. Due to its exposed location, divers will have the opportunity to see almost anything on this Similan dive including whale sharks and manta rays.

There is very little coral growth here except for green branching cup corals and orange sea fans, but the algae growth here is substantial, meaning a prolific amount of nudibranchs, including the twin magnificent sea slug and Spanish dancers. Leopard sharks are frequently seen as well as white-tip and black-tip reef sharks.

• Dive Type: Boat Dive
• Diver Level: Advanced Open Water Diver
• Max Depth: 35m

Tachai Pinnacle or Twin Peaks are a pair of submerged pinnacles located 500 m south of Koh Tachai. The southern pinnacle is bigger and is a dome shape surrounded by large boulders. To the west you will find large boulders, some of which have formed swim throughs. In the east, you will find stacks of small rock, most of which are cover by hard corals and sea whips. Colorful soft corals and sea fans dominate the northern area. The top of the pinnacle is a wide flat plain with bush and mountain coral. The smaller pinnacle comprises of a wide range of rock clusters and is home to large sea fans and corals, which are similar to the ones found in the southern pinnacle.
Manta rays visit this area for feeding and circling around the pinnacles. Some divers have encountered whale sharks as well. On the outer sand bed, divers can usually see leopard sharks, sometime three to four of them in the same dive. In addition, it is possible to find Jenkin’s rays, as well as whitetip sharks and blacktip reef sharks here as well. Swarm of chevron barracuda, bluefin trevally, batfish, snappers, and fusiliers are common here.

• Dive Type: Boat Dive
• Diver Level: Open Water Diver
• Max Depth: 18

The Boonsung Wreck is often described as ‘Fish Soup’. The density of marine life here is often better than most dive sites in the Similan Islands. An old tin mining vessel, surrounded by sand for miles in every direction, provides the perfect protection for thousands of juvenile fish. The schools of fish are huge and the variety of Macro life is one of the best in Thailand. This is a real divers dive site and part of a fascinating history of Tin mining in the Phuket and Khao Lak area.

The Boonsung Wreck is located about 5km West of Bangsak beach, to the North of Khao Lak. Visibility is typically not as good as the Similan islands. However, the huge variety of marine life makes it well worth seeing. It is a regular final stop on many Similan Liveaboards, although it is technically not part of the Similan islands. The Boonsung wreck also makes for an excellent and speedy day trip by longtail. The Boonsung Wreck is the best value dive around Khao Lak.

• Dive Type: Boat Dive
• Diver Level: Open Water Diver
• Max Depth: 19m

The wall, part of the Similan National Park, is decorated with various colorful soft corals and hard corals. From the ridge to the northeastern side are reefs that stretch along island. The reef slopes from a depth of 10m down to a sandy bottom at 25 - 30m. The majority of corals here are hard corals, including staghorn coral and brain coral that are interspersed with a few big coral heads. To the northwest of the island, there is a submerged pinnacle. The pinnacle is at a depth of 18 - 45m and is covered by an abundance of yellow soft corals and large sea fans. This site is a cleaning station for manta rays, so there is a high chance of finding at least one during a dive, particularly at the western ridge and northeastern outer reef. Koh Bon also has many kinds of sharks, such as leopard sharks and whitetip and blacktip reef sharks. Sometimes grey reef sharks swim by, and nurse sharks can be seen lying under coral heads. Schools of yellowtail barracuda, fusiliers, trevally, sweetlips and black and white snappers are all common in the area, as well as octopuses, sea snakes, and nudibranchs.

• Dive Type: Boat Dive
• Diver Level: Advanced Open Water Diver
• Max Depth: 45m