KOH BON
DIVING WITH MANTA RAYS
DIVING WITH MANTA RAYS
Koh Bon West Ridge is your best chance to dive side by side with a giant Manta Ray in Thailand. Although they can appear any time throughout the season, it is most common to see Manta Rays between January and March. The vertical wall extending out from Koh Bon bay leads into a massive ridge. The strong currents on top of the ridge seem to be a perfect playground for Manta Rays. Their inquisitive nature often brings them up close and personal with divers.
Koh Bon is located 25km North East of Similan island nine and 25km South of Koh Tachai. The ridge extends over 100m away from the Western tip of Koh Bon. The topography makes it a bit of a challenge, but it is possible to stay closer to the island. At just over 50km away from either Ban Nam khem pier to the North East or Thap Lamu Pier to the South East, Koh Bon is one of the easiest dive sites to get to from Khao Lak. To dive here from Phuket, the only option is a Similan Liveaboard.
OTHER NAMES | Koh Taloo, Koh Talu |
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THAI NAME | เกาะบอน, เกาะทะลุ |
LOCATION | Bon Island |
GPS | 8.5704, 97.6464 |
MIN LEVEL | Scuba Diver |
DEPTH | 5m – 40m |
VISIBILITY | 10m – 30m |
CURRENT | Mild to Strong |
HOW TO | Liveaboard & Day trip diving |
Koh Bon is instantly recognizable due to its unique shape and the fact it is Limestone whereas the Similan islands are exclusively granite. There are several interesting places to dive around Koh Bon, but the most famous and most visited is the West Ridge. This is where Mantas are most regularly seen. It is possible to spot Manta Rays anywhere around Koh Bon.
Koh Bon can get strong currents as the West ridge is very exposed. A good idea is to start the dive on the South side. Stay inside the bay for the first portion of the dive. The shallow reef has beautiful hard corals and a lot of marine life including the amazing reef octopus. Once you are comfortable you can head out to the West ridge a bit later in the dive.
During the Manta season it is not uncommon to get very close to a Manta Ray. It is possible to get excellent photographs so long as you do not chase or touch them. If you can get an identification photo (see ‘top tip’ below) this can be used for research and conservation efforts. If the ridge is busy, Mantas are also seen regularly on Koh Bon Pinnacle.
Although it may sound quite obvious, don’t miss the ridge. If you stay close to Koh Bon island and follow it around you can quite easily swim straight past it. Make sure you have enough decompression time and air left, as the ridge is between 20m-40m and stretches a good 100m away from the island. If there is current, it is still be possible to head out to the end of the ridge. Stay a bit deeper and close to the wall as this will give you more protection. During Manta season, spend as much of the dive on the ridge in order to increase your chances of a Manta Ray encounter.
A limestone island with a shallow bay to the South side and a sloping reef on the North. Koh Bon quickly gets steeper as you approach the Western ridge. On the South side is a large wall from the surface down to 30m. The ridge itself is between 20m-40m.
Only the harshest conditions can prevent you from diving at Koh Bon. It is the closest of the Similan islands to the mainland and there are many protected areas. Currents can be strong on the ridge, but this can be easily avoided if you dive in the bay.
In Manta Ray season this is most definitely a wide angle dive. You will get much better photos if the Manta Ray is relaxed and comfortable around you. Do not chase it! If you stay in one area it is much more likely the Manta Ray will circle around and come back for another look at you.
If you only have one dive at Koh Bon, it is probably best to stay on the ridge. But during Manta Ray season, one dive is not enough. Manta Rays can appear anywhere around the island. Koh Bon pinnacle is deep, but is another great place to find them. The North side of Koh Bon has several other outcroppings and smaller pinnacles. It also has huge areas of beautiful hard corals with lots of marine life (including Leopard sharks). The bay in the South is much shallower but also has healthy corals. Don’t do all your dives on the West ridge as there is plenty more to see around Koh Bon than just Manta Rays.
Liveaboard diving is the best way to experience the Similan Islands. Trips range from a single night to a full week on board. The optimum time to see all of the best sites is on a 4 night Similan Liveaboard including the amazing Richelieu Rock.
Above are a few of our favourite Similan Liveaboards. But, we understand that sometimes there is just too much choice. So, if you are not sure what it is you are looking for, please contact us for more advice.
If currents allow, the best place to jump is at ‘The Waterfall’, as it is so close to the West ridge. In the photo below you can see the island gradually sloping off the the left (West). This slope continues underwater and forms the basis of the ridge. About 30m before the sloping rocks descend under the surface, there is a small hole in the island. Do not get this confused with the much larger hole at the back of the bay (seen on the right). ‘The Waterfall’ is much smaller, but big enough to allow water to come splashing through. This creates the small waterfall effect (‘Naam Tok’ or น้ำตก in Thai) and this marks the best place to jump. The larger hole in the island (on the right) is where the common Thai name ‘Koh Talu’ comes from. ‘Koh’ meaning island and ‘Talu’ literally translates as ‘through’.
As you descend next to the waterfall, it is worth looking back up to the surface. When the water comes crashing down it creates a dramatic white water effect above you and makes for a great start to the dive. From here you can start to get a bit of depth next to the wall. Head West along the wall and look inside the cracks in the limestone. This is a good place to find Moray eels, nudibranchs and sponge snails. Also remember to look out into the blue, as there are often huge schools of Trevally, Rainbow runners, Long nose Emperor fish and Manta Rays. The deeper part of the wall has some beautiful hard corals and this leads you out to the ridge.
If Manta Rays are around, or even if you think they might be, this is where you should spend the majority of your dive. If the current is strong then drop a bit deeper and stay next to the rocks for a bit of protection. This should allow you to swim all the way out to the far end of the ridge. The deeper part of the ridge is also home to the most beautiful corals. If the current is not too strong you can shallow up to the top of the ridge. If Manta Rays are around, they will often circle around the top of the rocks. Don’t follow them out into the blue as this will scare them off the dive site and they may not come back. Have patience. There is a good chance they will circle around and come back.
When you start to run low on deco time you can head to the North part of the dive site. There is a huge orange coral head at around 18m full of shrimp and often covered in glass fish. The North side is also a great place to look for octopus, Napoleon wrasse and banded sea snakes. You can either keep heading East along the North side, but most divers turn back around to do their safety stop near the ridge. This gives you one more chance to see a Manta Ray flying past. Swim out into the blue for your safety stop and let the current take you away from the island. Make sure you use a safety marker as there can sometimes be a lot of boats around Koh Bon West Ridge.
Use this route at slack tide or when the current is moving to the North.
Jump in next to ‘The Waterfall’. Descend next to the wall and start swimming West towards the ridge.
If the current is strong you can stay deep and near the rocks. This way you are able to swim out along the ridge.
If visibility is not good divers can swim straight past the ridge without realizing it is there. Keep checking this heading and follow it all the way to the end of the West ridge.
Once you have passed the ridge you can keep heading along the North side until you reach the ‘Second Ridge’. It is also fairly common to see Manta Rays here.
You can finish the dive on the North side, or if you still have enough air, swim back to the ridge. Manta rays can come and say one last goodbye if you do your safety stop near the ridge.
Take a look at one of the other amazing Similan Dive Sites below, or go back to the Interactive Map.
Koh Bon west ridge is the most famous dive site in all of Thailand for encounters with the giant Manta Ray. Although it is possible to see them at Koh Tachai, Richelieu Rock and around the Similan islands, Koh Bon is by far their favourite place to visit. The island itself is very different from others in the area. The topography and strong currents seem to attract the Manta Rays. It is a truly unforgettable experience. If you do get lucky, this is sure to be the highlight of your Thailand diving holiday.
There are two types of Manta Ray; the giant and the reef. It is the Giant Oceanic Manta Rays (Manta Birostris) that are frequent visitors to Koh bon. There have been no recorded sightings of the reef Manta (Manta Alfredi) in the Similan Islands. As the name ‘Giant Manta Ray’ suggests, they are the larger of the two species and they are pelagic. This means they cover great distances and don’t stay in one place for long. This makes the experience of diving with a Giant Manta much more special, as it is never guaranteed to see them. It depends on the time of the season and a certain amount of luck. The ocean is not a zoo.
The strange shape of the island and its outcroppings create strong currents for the Manta Rays to play in.
Staying calm and imitating Manta Ray behaviour can sometimes draw them much closer to you.
Manta rays are filter feeders and gentle giants. These leviathans are nothing to be afraid of but they deserve to be treated with respect. Manta rays have the largest brain size relative to their body of all the fish in the ocean. They are very intelligent and curious animals. If you stay calm and DO NOT CHASE THEM, they are more likely to circle round and come back for a better look at you.
At Scuba Diversion, we dive with scientists from the Marine Megafauna Foundation on our exclusive research and conservation trips. They have given us a few tips for diving with Manta rays. Firstly, if you stay below their eye level, it can make them feel more comfortable around you. This makes Manta Rays more likely to come close.
Secondly, as they are so intelligent, there are things you can do to increase their interest in you. If you imitate their wing flapping movement with your arms you may be surprised what happens. Wave your arms up and down at the same time as the Manta Ray, and they might just come and have a look at you. Eye contact with a four meter Manta Ray is a humbling experience. One great reason for flapping your arms up and down is quite simple; it looks hilarious.
The best time to see Manta rays is typically between January and April. However, it is possible to see them any time the Similan Islands National Park is open (mid Oct to mid May). Currently not that much is known about Manta Ray behaviour. At Scuba diversion we continue to work with several scientists to help progress new understanding about their behaviour.
For a truly unique experience you can join our yearly Manta Ray Discovery expeditions to Myanmar (formerly Burma) or other World class destinations including Raja Ampat, Indonesia and Socorro, Mexico. Led by top scientists, we will be using up to date tagging research to find new Manta Ray Aggregation sites in the unexplored Northern extremities of the Mergui Archipelago.
Even as a recreational diver you are able to contribute to science. Identification photos can be used to track their movements and this can help in conservation efforts. Participation from dive centers worldwide has already had an impact on creating Manta Ray sanctuaries. To dive with Manta Rays in Thailand, or to learn how to take get involved with identification photos, please contact us.
Photos of the underside of a Manta Ray can be used to identify them.
There is no better way to see the Similan Islands than by diving on a Similan Liveaboard. They offer the best overall value and range from just a single night to a full week on board. Enjoy supreme comfort, delicious food, and the best diving in Thailand.
Our new Similan Islands Dive Site E-book Guide features full colour maps and key facts about the dive sites you will likely visit on your Similan liveaboard. Download it for free and take it with you on your mobile or tablet as the perfect trip companion.
Off the Chart Expeditions lift a typical scuba diving liveaboard to new and exciting levels. Born out of a passion for exploration and a long history of enjoying life on dive boats. Our bespoke expeditions offer what we consider to be the ultimate dive trip.