Koh Bon The Ridge - Liveaboards Phuket

Koh Bon - The Ridge

Koh Bon – The Ridge

At a Glance

•    Max depth: 40 meters
•    Level of difficulty: Open water upwards.  
•    Visibility: 10/40 meters
•    Current: Moderate to strong
•    Season: October through June


Koh Bon -The Ridge, one of the best dive sites in Thailand, is a large island to the north of the Similan Islands and both Liveaboards and Day Trip Boats come here – it is known as one of the best dive sites for Manta Rays.

There are two sites here, The Ridge (this page) and Koh Bon Pinnacle which is a series of deep underwater pinnacles.


There is a small bay which is protected by the high limestone walls of the island and is an excellent place to do a sunset or night dive. Actually, several boats favour here to spend the night.


Many moons ago there were extensive coral beds here, unfortunately, they have been destroyed by dynamite fishing and all that is left on the far side is a bed of smashed corals.


However, do not be disheartened too long, as this site is coming back slowly and surely. It is still an amazing and rugged dive site with some serious action going on, the fish life is wonderful. Although not the easiest of sites, the currents can be testing and it is quite deep,  


As previously mentioned, Koh Bon is a unique island giving you one of the best chances to catch a glimpse of the huge pelagic Manta Rays -that come here to feed and be cleaned. 

Below is an excerpt from my log book which will give you a great idea of what this site is all about:

After dropping down to a depth of 23 metres we were encircled by a voracious school of Small Tooth Emperor Fish. They may have little teeth they still meant business though and the small fry needed to be careful.

Also tailing them were a crack team of Bluefin Trevallies, these guys are opportunistic feeders and generally work in small packs, very fast attacking fish.

As we watched in awe at the sheer ferocity of the little predators, most did not notice that we were gently drifting out to the edge of the Ridge. The water started to turn a little turbid due to the warmer water mixing with the cooler.

The ridge at this point drops off quite quickly and if you do not grab on to the ridge then you can find yourself drifting way off-site, and if there is a current, it can be quite difficult to get back.

As we hung onto the ridge for a breather, she appeared from out of the blue like an alien craft. She had quite clear markings of Black and White a four-metre Manta Ray glided by us. 

Ten minutes she was there entertaining us, fly by after fly by. A perfect specimen of one of the biggest fish in the sea graced us with its presence. Remind me to thank the Gods of the sea. A check on the air gauges showed us that we needed to start to make an ascent.

So it’s a huge thank you to Koh Bon for another amazing dive with another Manta sighting. So far this year there have been more sightings than the last few years combined. We set sail for Koh Tachai and dream what wonders await us there.


Some of the other fish we saw on that site today were black and white tip reef sharks, snapper, barracudas, Trevallies, triggerfish and coral banded sea snakes Scorpion Fish, Napoleon Wrasse, Fusiliers, Blue Fin Trevallies and Emperors.

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Manta Ray