Green Rock is on the north west tip of Koh Nangyuan and consists of unusual boulder formations that form a number of adventurous swimthroughs, which makes this one of the most interesting sites around Koh Tao.
The deeper parts of the site go down to around 28m for experienced divers and beginners and students can stay in the shallower waters alongside the island at around 10m.
You will find an abundance of beautiful parrotfish, white eyed morays, blue spotted stingrays and angelfish. Green Rock is also a good place to see green and hawksbill turtles and there are a number of resident  yellow-margin and titan Triggerfish, which use the sandy areas around the rocks to nest.