Koh Bon Similan National Park

Koh Bon within the Similan National Park is an advanced dive site famous throughout the diving world as one of the most reliable locations in Thailand for manta ray encounters. This small rocky island on the northern boundary of the Similan archipelago creates an underwater cleaning station where mantas arrive to have parasites removed by resident cleaner wrasse, offering divers the extraordinary privilege of watching these majestic creatures at close quarters. The island's western ridge is the primary dive area, a reef that slopes from the shallows to considerable depth along a rocky wall. The advanced rating reflects the combination of depth, current exposure, and the open-water location that can present challenging conditions. The currents that sweep around Koh Bon are precisely what make the site so productive for manta encounters, as these same flows bring the plankton that draws the mantas to the area. The manta cleaning station is located along the western wall, where a specific section of reef hosts the cleaner fish that provide the service mantas travel to receive. When mantas are present, the protocol is clear: descend to the reef, find a stable position, and wait. The mantas arrive on their own schedule, and the experience of watching a manta ray with a wingspan exceeding four meters glide in and hover over the cleaning station, seemingly oblivious to the awestruck divers below, is one of the most powerful wildlife encounters available anywhere in the world. Beyond the mantas, Koh Bon's reef is spectacular in its own right. The wall is decorated with colorful soft corals, large sea fans, and barrel sponges that create a vivid backdrop for wide-angle photography. Hard corals are healthy and diverse along the shallower sections, and the fish community is robust. Schools of trevally, fusiliers, and barracuda patrol the reef edge, while Napoleon wrasse, groupers, and moray eels inhabit the wall's many crevices and overhangs. The deeper sections of the wall may reveal encounters with leopard sharks resting on sandy ledges, and reef sharks occasionally cruise past in the current. The combination of charismatic megafauna, exceptional reef health, and dramatic underwater topography makes Koh Bon one of the most action-packed dive sites in the Similan chain. Koh Bon is visited on multi-day liveaboard trips through the Similan Islands, and it is invariably one of the most anticipated stops on any itinerary. The season runs from October through May, with manta encounters most likely from January through April when the oceanic conditions are optimal. Koh Bon exemplifies why the Similan Islands are considered a world-class dive destination. The near-certainty of manta encounters combined with the outstanding reef diving creates a site that delivers memories lasting a lifetime and gives divers a compelling reason to return to Thailand's Andaman Sea again and again.