KO BON, KO TACHAI, MU KOH SURIN & RICHELIEU ROCK

North of the Similans lie Ko Bon, Ko Tachai, the Surin Islands National Park, and Richelieu Rock.

Ko Bon: The Perforated Island

Ko Bon is located about 20 kilometers north of island #9 and features one of the only vertical walls in Thailand. The main dive site is on the southwestern point and consists of a 33 meter wall facing the small cove, and a step-down ridge that carries on to depths of over 45 meters. Leopard sharks are common on the ridge and on the sandy flats below the wall. Although the soft corals are not as high-profile as they are in the Similans, the colors of the corals are radically different and include shades of turquoise, yellow and blue, besides the more common pinks and purples. Ko Bon is one of the better places to see manta rays, almost all year around. There is also a pinnacle in the bay just to the north of the ridge. It's a deep rock, but if you're an experienced diver it's worth the short bottom times you'll get (especially if you're on a longer trip). It's larger than Richelieu Rock at the base, and a hard swim. The bottom is over 40 meters deep, and the top only come up to about 18-20 meters.

Ko Tachai

Twenty-five kilometers north of Ko Bon, Ko Tachai has an offshore underwater ridge that runs perpendicular to the island. This is considered to be one of the finest dives in the Kingdom of Thailand and is famous as a place to see not only the more common species of corals, fans and tropical fish, but larger animals such as rays, leopard sharks, nurse sharks and hawksbill turtles. Whale sharks and manta rays make an appearance on a regular basis. Tachai also boasts a breathtaking sandy beach on its northeastern shore; a great place to hang out and feel like Robinson Crusoe.

Mu Koh Surin National Park & Richelieu Rock (Hin Bonam)

The Surin Islands, although visited by several dive operators from Phuket, are more appropriately famous for their beautiful coves, bays and dense jungle than they are for their diving. Spending a few idyllic days on a sail boat or other yacht here are the stuff dreams of paradise are made of yet the serious diver will be bored easily after a few dives because of the generally poor visibility and lack of fish. The key to having a good dive here is with our knowledgeable guides to show you the highlights.

Surin's ace card, however, is a small submerged rock about 18 kilometers east of Surin. Richelieu Rock, just exposed at the lowest of tides - thus a navigational hazard for those boats not equipped with a GPS navigation system - rates as one of the best places in the world for swimming with our gentle giant, the whale shark.

Encounters with these fish - the largest of all fish - are rare almost any place in the world. But for some reason, Richelieu attracts more than its fair share. Swimming with such a large animal, known to grow to lengths of 20 meters or more, has to be a high point for any diver. Sightings occur often, but unfortunately less often than in the 1990s, depending on the time of year.

Generally, February, March and April are the best times for a visit. The big difference between diving here and other areas that are famous for whale sharks, such as Western Australia, is that spotter planes are not needed as the sharks cruise around the rock, and the visibility is normally excellent. Who knows why they are here, but the sharks aren't around because of plankton blooms like in Australia. Thus, clear water.

What Richelieu Rock has really become famous for recently are the incredible numbers of unusual critters. The dive masters are now quite good at spotting ghost pipefish, Harlequin shrimp, and tigertailed seahorses. If you don't see something weird here you just aren't paying attention. Cuttlefish hover around, usually in the fall, but very often anyway, octopus are common, and lionfish as well as different kinds of anemone fish are easily spotted.

Richelieu Rock is a world-class dive site, and if you don't like diving here, you simply don't like diving. You can dive here over and over and see something new.