Similan National Marine Park
23 kilometers northeast of the nine Similan Islands, Koh Bon stands alone in the Andaman Sea and represents a very different experience from the huge granite formations found in its neighboring islands in the southwest.
Although not one of the nine Similan Islands, Koh Bon is a member of the Similan National Park – having been added in 1998.
This dramatic islet made of sedimentary rock looks to have been pushed up from the sea bed, exposing banded layers of uneven rock. Time and weathering has created many caves and small caverns on the steep faces of the bay and north ridge. So much so, in fact, a large hole has been carved out in the northwest corner of the bay, making it possible to see right through that portion of the island.
There are three main sites to Koh Bon – The West & North Ridge, The Pinnacle, and The Bay.
The West and North Ridge are the most popular dive sites and usually explored in turn, depending on the direction of the current. Entering the water from the West Ridge presents a sheer wall that you can follow to the ridge itself. The ridge stems from the island and continues underwater, dropping down into the depths. Decorated in many soft corals you can find an assortment of marine life in and among the nooks and cracks, including moray, octopus, cowrie, and the curious looking sponge snail. As you descend, large napoleon wrasse are a common sight along with schools of snapper, barracuda, fusiliers, and trevally. From the North Ridge, a reef slopes down from around 10 meters to where staghorn and brain coral are typical and a number of large coral heads scatter the floor.
Most famous for its migratory visitors the Giant Manta Ray, Koh Bon is the number one place in Thailand for divers and snorkelers to see these magnificent animals. Typically arriving in the New Year, these gentle giants love to circle around the west ridge, making for some very close and unforgettable encounters!
Koh Bon Pinnacle is located a few hundred meters north of the west ridge and is locally know as Hin Luang (yellow rock) due to it being covered in yellow soft corals and sea fans. Starting at 18 meters and descending to 40 meters the site is best dived in favorable conditions when the current is not too strong. Worth the effort, as marble rays and spotted eagle rays, and, of course, the Giant May Ray can be seen in addition to the usual suspects.
The bay offers sheltered waters, making it ideal for snorkeling, ‘try’ dives, and shallow course exercises. Snorkelers can easily reach the west ridge from here if the giant manta are putting on a show and the bay itself is home to many varieties of life, such as, batfish, morays, sea snakes, octopus and the occasional turtle.