North of the Similan Islands lies Koh Bon, Koh Tachai and the Surin Islands including Richelieu Rock. All islands offer a class of diving vastly different from that experienced at the Similans and if you're after the big fish, then it shouldn't be missed.

Koh Bon
Located 20 km north of the Similans Koh Bon is famous for the natural perforation carved through the island. The southwest dive site is a sheer wall 35m deep followed by a stepped ridge descending to 45m. Leopard sharks are sited on the ridge and sandy flats below. Koh Bon is noted as one of the better places to experience the majesty of diving with manta rays.
Koh Tachai
About 25km north of Koh Bon, Koh Tachai's lush tropical foliage runs over granite to a beautiful sandy beach. Tachai is famous for an underwater ridge that juts out at 90 degrees to the island. Tachai offers Rays, Leopard Sharks & Nurse Sharks.
Koh Surin and Richelieu Rock. The surin islands although rather beautiful topside are rather boring below the waves. Richelieu Rock, however, is one of the best places in the world for encountering Whalesharks.
Richelieu Rock
• Horseshoe Shaped Pinnacle
• Hard & Soft Corals
• Whale Sharks, Numerous Tropicals, Barracuda
• Moderate Currents
• 10 to 30 Meters Visibility
• Advanced Divers
This horseshoe shaped rock located near the Surin Islands in the Andaman Sea, is considered by many to be the best dive site in Thailand. Discovered by diving pioneer Jacques-Yves Cousteau with the aide of local fishermen, it now attracts divers from all over the world due to the sheer variety of marine life that can be seen here.
Schooling Chevron Barracuda, numerous types of Moray Eels, abundant LionFish and Scorpion Fish. 5 types of Anemone Fish, Juvenile Emperor Angel Fish, Sea Horses, Ornate Ghost PipeFish and Harlequin Shrimps can all be found. This site is also a prime location for sighting Whalesharks, occasional Manta Rays and ShovelNose Rays.
Richelieu Rock should be a must on every divers list. Regardless if you're a macro enthusiast or passionate about bigger creatures it has something for everyone.