Dive Koh Bon
Koh Bon is located about 20 kilometers north of Island 9 and features one of the only vertical walls in Thailand. The island has no beaches and is in the shape of a horseshoe – forming a protected cove that shelters dive boats and divers from prevailing winds and currents.
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 sandy flats below the wall (particularly on the eastern side). 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. With the angles on the wall, they also offer an ever changing spectrum of colors and make for some great photos around noon.
Koh Bon Ridge is one of the best places to see manta rays, almost all year around. This last year featured Mantas almost everyday from mid-December until April. Frequent, but not daily sightings for the rest of the season!
In addition to the large marine life, be prepared for the little stuff too! Great Nudibranchs litter the cracks of the wall and exciting treats like Pipefish, Hawkfish and even Frogfish are here.
Diving Depths of 1- 35 meters (1-100 feet), with most time spent on the ridge at 20-25 meters (70-85 feet). Visibility runs about 20 meters (75 feet) but gusts of cold water, with associated plankton blooms are not uncommon. Currents can be mild to strong, depending on tides.
It is also common to have virtually no current inside the bay but a ripping current on the outside. Experience level: while beginners can do this site, it is recommended that the diver be intermediate and above due to lack of beaches, potentially strong currents and popularity of the site.
As with all dive sites in the Similan Isiands, it is strongly recommended that you go with only registered and reputable dive operations, carry suitable travel insurance that covers diving accidents and evacuations as well as trip cancellations insurance due to the potentially erratic weather conditions.
In March and April 2010 the Similan Islands suffered from a naturally occurring event called the Reverse Indian Ocean Dipole. This is very similar the “La Nina” that changes water temperatures and currents in the Pacific ocean. In this case, the water temperatures in the entire Andaman Sea were raised between 2 or 3 degrees above median. This was enough to damage the living corals in shallower sites and those with limited tidal interchange. On the Western facing side of the Similan National Park, the affect on the sites was minimal. On the shallow sloping reefs of the Eastern side , there was a more noticeable impact on the corals. His has caused some bleaching, and on two of this sites a – a noticeable impact. The National Park system shut down several sites throughout the Andaman region to protect the reefs from potential human impact (diving, snorkeling and fishing). These sites are already showing regrowth and at least two of the sites have re-opened at this time.
Plus understand that the bleaching is not the result of direct human impact, or over use. It is the results of vast climactic changes that are happening on our globe. The reefs are accustomed to these temperature changes and can easily adapt and regrow. They can not regrow from the damage done to them physically or chemically by inconsiderate divers and snorkelers.