Dive Site: Koh Bon

About Koh Bon

Koh Bon is a distinguished dive site located north of Similan Island No. 9, within the same national park administration, though geographically distinct as a limestone island compared to the Similans' granite formations. It is celebrated for its incredible marine biodiversity and stands out as a prime location in Thailand for encountering majestic Manta Rays, especially along its prominent ridge. The island's remote, uninhabited nature means all diving is boat-based, providing an exclusive and often less crowded underwater experience. The main dive site, Koh Bon Ridge, lies on the southwestern corner, featuring a dramatic vertical wall that transitions into a sloping hard coral garden. This unique topography offers varied habitats, from deep wall sections adorned with soft corals and anemones to shallower, pristine hard coral formations teeming with reef fish. The ridge itself consists of large, step-like rocky formations covered in diverse soft corals, creating a visually stunning environment that descends to depths of around 35 meters. Marine life at Koh Bon is abundant and diverse, with regular sightings of pelagic species drawn to the nutrient-rich currents. Manta Rays are a major highlight, frequenting the ridge area which functions as a large cleaning station. Divers can also expect to encounter Leopard Sharks, Nurse Sharks, various moray eels, triggerfish, lionfish, sweetlips, octopus, and the occasional Banded Sea Krait. Whale Sharks and Eagle Rays are also spotted, particularly during the peak season. Diving at Koh Bon involves navigating currents, which can range from mild to strong, especially around the ridge. Divers typically begin their exploration in the more sheltered bay area before moving along the wall and then to the exposed ridge. The site offers opportunities for drift diving, allowing divers to experience the dynamic underwater landscape and its resident marine life as the current carries them along. Night dives are also possible in the cal

Dive site facts: Koh Bon

Depth

0–45 m

Current

Moderate to very strong

Visibility

20–40+ m

Water temperature

27–30°C

Entry

Boat / negative entry

Level

Intermediate to advanced, current experience helpful

Dive type

Wall, slope, drift, pelagic encounters

Night dive

Possible in sheltered bay

Region / port

Similan Islands, Andaman Sea

Coordinates

8.9234, 97.8567

Conditions & Currents

Currents at Koh Bon range from moderate to very strong, particularly around the exposed ridge where they attract large pelagic species. Divers typically commence their dive in a more sheltered bay area before transitioning to the wall and then the ridge, allowing for a drift dive when conditions permit. Strong currents necessitate careful dive planning, often involving negative entries to avoid being swept away from the boat. Experienced dive guides proficient in reading currents are essential, and divers should maintain excellent buoyancy control to navigate the varying flow. Visibility typically remains high even with strong currents, which replenish nutrients and clear the water, but can also cause surge near the surface or along the reef.

Marine life & sighting chances

Manta Ray

November-April · common

Leopard Shark

occasional

Nurse Shark

occasional

Moray Eel

common

Triggerfish

common

Lionfish

common

Sweetlips

common

Octopus

occasional

Banded Sea Krait

occasional

Whale Shark

February-April · rare

Eagle Ray

occasional

Trevally

common

Tuna

common

Snapper

common

Dive profile & how the dive runs

Dives at Koh Bon typically commence near the sheltered bay on the south side of the ridge. Divers descend along a vertical wall, which gradually transforms into a sloping hard coral garden at around 10-12 meters. This area is rich with diverse reef fish and features pristine coral formations. From here, the dive progresses towards the famous ridge, where the topography shifts dramatically to large, step-like rocky formations descending to approximately 35 meters. These steps are adorned with soft corals and are frequented by pelagic species and Manta Rays. Divers are advised to keep an eye towards the blue for larger marine life. The current can be strong on the ridge, often facilitating a drift dive around its northern side, where the bottom returns to a hard coral slope with scattered rocks. Safety stops are usually conducted in shallower, calmer areas of the reef or bay, depending on current conditions and diver preference.

Underwater photography

Koh Bon offers exceptional opportunities for wide-angle photography, especially when Manta Rays are present. A fisheye or wide-angle lens is ideal for capturing their majestic presence in the blue, as well as the expansive coral gardens and dramatic wall sections. For macro enthusiasts, the wall and coral slopes harbor a variety of smaller subjects, including nudibranchs, crabs, and cleaner shrimp, requiring a macro lens. Due to variable currents, maintaining stable buoyancy is crucial for sharp images. Consider using strobes to bring out the vibrant colors of soft corals and anemones, especially at deeper sections. Be mindful of Manta Ray etiquette; avoid chasing or crowding them, and maintain a respectful distance to allow for natural behavior and optimal photographic angles.

Combine with nearby dive sites

• Koh Bon — West Ridge

  An exposed pinnacle suitable for experienced divers, known for potential Manta Ray sightings and strong currents.

• Richelieu Rock

  Thailand's most famous site, known for whale sharks and abundant marine life, typically visited on Surin Islands liveaboards.

• Hin Muang

  Part of a southern Andaman Sea itinerary, featuring large vertical walls and Manta Ray encounters.

• Hin Daeng

  Known for Thailand's biggest vertical wall, red and purple corals, and sightings of Grey Reef Sharks and Manta Rays.

• Elephant Head Rock

  A Similan Islands pinnacle with swim-throughs, boulders, and medium to strong currents.

Getting there & logistics

Access to Koh Bon is primarily via liveaboard trips that depart from Khao Lak or Phuket, typically as part of a Similan and Surin Islands itinerary. Khao Lak is approximately 80 km northwest of Koh Bon, while Phuket is about 200 km south. International flights land at Phuket International Airport (HKT), from where transfers to Khao Lak are available. Liveaboard trips typically range from 4 days/4 nights to 6 days/6 nights during the high season, which runs from November to April. Koh Bon is part of the Similan Islands National Park, meaning park fees apply and the area is closed to visitors from May to October.

Safety & environment

The nearest recompression chamber is located in Phuket, necessitating prompt evacuation in case of a dive emergency. Divers should ensure they have comprehensive dive insurance that covers emergency medical treatment and evacuation, especially given the remote nature of the site. Strong and unpredictable currents are a significant hazard at Koh Bon, requiring divers to possess advanced buoyancy control and experience in drift diving. Always follow your dive guide's instructions and maintain awareness of current direction and strength. Employing surface marker buoys (SMBs) is crucial for signaling the boat after surfacing, particularly in active current areas. Marine life, such as Banded Sea Kraits and Lionfish, should be observed from a respectful distance without touching.

Who it suits — and who it doesn't

FAQ

Koh Bon FAQ

Liveaboards diving Koh Bon

These liveaboards may visit Koh Bon on selected itineraries — the exact dive sites depend on departure, weather and conditions.

Mandarin Queen 9

Thailand

26 guests37.5 m

Manta Queen 8

Thailand

24 guests

$127/day

The Junk

Thailand

18 guests33 m

$163/day

Deep Andaman Queen

Thailand

23 guests30.5 m

$194/day

Explorer

Thailand

16 guests25 m

$150/day

Andaman

Thailand

20 guests26 m

$108/day

Stingray

Thailand

8 guests24 m

$245/day

Seatopia

Thailand

24 guests24 m