Although the granite inlet is isolated to the northwest of the Similan islands, Koh Bon is still considered to be part of the Similan National Park and south of Richelieu Rock.

One favorite dive spot is the western ridge of the island, which falls steeply to the deep sea.

Above the surface there is an opening where you can walk through to the other side.

   
Diving boats usually park in a bay located south of the ridge, where they have a maximum protection against wind and strong waves.
Underwater topography in the southern bay comprises hard corals including mountain coral and brain coral.

The western ridge continues from the main land out to the sand bed to a depth of more than 35 to 40 meters.

The walls are decorated with various colours of soft corals and a few hard corals.

From the ridge to the northeastern side are reefs that stretch along the island.

The reef slopes from a depth of 10 meters down to a sandy bottom at 25 to 30 meters.

The majority of corals here are hard corals including staghorn coral, brain coral that are interspersed with a few big coral heads.

Some areas are made of flat plains with sparse corals.

800 meters to the northwest of the island, there is a submerged pinnacle, which is sometimes marked by a buoy, although it is often washed away Thus, a depth finder is essential here.

The pinnacle is at a depth of 18 to 45 meters and covered by an abundance of yellow soft corals and sea fans.

Varies from moderate to strong. In particular, current fluctuations occur near the ridge.

When the current crashes against the walls, there can be down welling currents that sweep out into the open sea.

This site is a cleaning station for manta rays, so there is a high chance of finding at least one during a dive, particularly at the western ridge and northeastern outer reef.

Koh Bon also has many kinds of sharks and white-tip and black-tip reef sharks.

Sometimes grey reef sharks swim by, and nurse sharks can be seen lying under coral heads.

Schools of yellowtail barracuda, fusiliers, trevellies, sweetlips and black and white snappers are all common in the area, as well as octopuses, sea snakes, and nudibranchs.

Manta rays have a distinct circling behavior when feeding on plankton.

You can experience and see this for yourself unless you chase them or swim too close, which may make them panic and swim away.

Chasing them also wastes your air supply and reduces the chances for other divers to encounter these spectacular creatures.

Because Koh Bon Pinnacle is a deep site with the top at 18 meters, you should be cautious about no decompression time.Divers can swim back to the reef of the main island if the current is not too strong (by setting your compass to the southeast).

Be aware that it would take about 10 to 15 minutes to swim in blue water. On the other hand, it is difficult to swim from the reef to the pinnacle because the pinnacle is quite small.

The pinnacle is suitable for experienced divers only.