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Diving Thailand – Dive Sites Thailand – Scuba Diving Similans
Name Koh Tachai Similans
Depth 10-50m
Vis 10-30m
Water Temp 26-29c
Level Intermediate+
Our Rating 4.2 Stars
Best Time to Visit October to May
GPS 09-03-449N 97-48-789E
  Map of Similan Islands
Whaleshark Koh Tachai Thailand

North of Koh Bon by about 21km, lies the island of Koh Tachai. Tachai Pinnacle is also sometimes referred to as 'The Dome', or 'Twin Peaks'. The sandy bottom to the north is at around 40 metres and slopes down gradually to more than 50 metres. The most southerly of the twin pinnacles tops out at about 12 metres. It is shaped like a huge dome and is encircled with boulders and rock formations. There are many gorges and swim throughs dotted around, making great homes to groupings of Oriental Sweetlips and Groupers.

White Whip Corals dance in the currents, which can sometimes be ripping at this dive site! It's about a 50-metre swim to the smaller northern pinnacle, which tops out at 18 metres. Manta Rays are also habitual visitors to Koh Tachai and are often spotted while carrying out a safety stop on the buoy line. In recent years there has been an increasing number of Whaleshark sightings here, some years rivalling the numbers that grace Richelieu Rock further north. Koh Tachai is literally teaming with marine life. Pelagics school around this dive site in huge numbers!


Smaller critters like Ghost Pipefish, Frogfish and Long Nosed Hawkfish abound - it's definitely worth sticking with your experienced dive guide, so they can show you all the treats this site has to offer.  They can also guide you around the site with the least interference possible from the currents.

This site isn't for inexperienced divers and there are few other dive sites in Thailand with currents to rival the ones found here. Stay close to the topography and hide from the currents where possible. Descend and ascend using a mooring line, remembering to do your safety stop on the way up. It is cautious for all divers to carry a submersible marker buoy, in case you drift too far from the buoy line and need to ascend. This not only helps to avoid being run over by passing boats, but it's also much easier for dive boats to identify divers on the surface - who may be drifting away from the dive site in a strong surface current.