Koh Tachai pinnacle is 20 km north of Ko Bon. Its one of the best Northern dive sites in the Similan Islands and one not to be missed. It consist of twin peaks. The southern pinnacle is larger. It starts at 12 meters and most likely you will use a mooring line to reach this site. Some Dive shop called this The Dome Because of its shape but most call it Koh Tachai pinnacle. It is a boulder dive on the deeper side but in the swallows there are a host of hard and soft corals. The northern pinnacle is a 50 meter swim away. Deepest part 40 meters
The chances of spotting giant Manta Rays and Sharks are huge on this dive site. This is a solitary island, so you can never tell what will pass by. The swallow part of Koh Tachai is beautiful. Lots of soft / hard corals, giant sea fans schools of barracuda, trevails. A Whale shark family was spotted many time here with giant manta ray swimming through them. Best Dive I have every had was at Koh Tachai Pinnacle.
Intermediate to very strong – Northeast to southwest direction.
10 – 40 meters thermocline (aka the green monster) that can reduce visibility in some places but you don’t usually get thermocline here.