Manta Ray at Koh Bon
Below is a good video to show you what the snorkeling is like at Koh Bon. Basically if you see manta rays it’s great, if not it’s pretty average.
The first point to make is that this video was filmed by snorkelers on a dedicated snorkeling liveaboard called the Sawan “aka Reggae Queen” that spends 3 days and 3 nights at Similan, Surin, Koh Bon and Koh Tachai. They consistently see manta rays. The day trip boats very rarely see manta rays.
The second point to note is the depth of the water. The mantas tend to congregate around a submerged pinnacle off the west tip of the island. Sometimes they stay shallow, sometimes they go deeper (this one is deep) but the water is usually clear and they can be easily seen from the surface. If you can duck dive you can swim down with them. What you won’t see while snorkeling at the pinnacle is any coral, it’s beyond snorkeling depth. So if the manta rays don’t show up you will just be looking at blue water. Sometimes you need to be patient and wait. And wait and wait. Manta’s don’t call ahead to warn of their arrival and they don’t don’t make a noise either. There is some coral to see in the bay and the reef walls leading out to the pinnacle (it really comes alive at night when all the tube worms open up) but for most people it’s the mantas that they’ve come to see.
If you are not comfortable swimming in open water you will not like Koh Bon. Currents can also be strong, the mantas love the currents. You may find yourself drifting away from the pinnacle and have to constantly swim back. If you think you are a powerful swimmer try keeping up with a manta ray.