One of the best dive sites the Gulf of Thailand has to offer, Sail Rock sits in between Koh Tao and Koh Phangan (closest to Koh Phangan). Dive centers from Koh Tao, Phangan & Samui all visit the dive site regularly so it's easy to get to. Being the largest pinnacle in the area, Sail Rock attracts a ton of marine life, from big schools of fish to awesome macro critters.
Sail Rock is the only deep pinnacle dive site in the area that actually surfaces, and the rock reaches a few good meters above the water line. This makes it more accessible to divers of different levels, and some dive schools even teach discover scuba courses here! While diving at the shallow parts of Sail Rock is great, there is so much more to explore at the deeper parts.
Big schools of jacks (big eye trevally), chevron & pickhandle barracuda, fusiliers and batfish all make Sail Rock their home with schools sometimes reaching thousands. Other interesting marine life includes whale sharks, giant moray eel and giant groupers.
On the north face of the dive site you'll find a vertical chimney or swim-through. With 3 entry/exit spots at 6 - 12 & 18 meters, it's a great way to ascend or descend. For the more advanced divers there is a 'secret pinnacle' of the east wall, which is where the big schools of jacks often hang out. The west has quite steep walls while the south gradually slopes out.
Sail Rock normally has good conditions with 10-15 meter visibility, and at times great conditions with visibility exceeding 30 meters. Generally conditions drop around full moon and due to it's location far off the coast and away from islands, trips can be cancelled due to bad weather.
Regardless, it's easily one of the best dive sites in Thailand and if you find yourself in the area it's well worth the visit!