Also called: Hin Keo
Green Rock is off the northern-most tip of Koh Nang Yuan. Depending on the currents, which generally aren't strong, you can dive either side of the point. The main attraction here are the many dive-throughs, which range from the easy to the ever-so-slightly tight squeeze.
You will see much the same marine life as found around the other Koh Tao dive sites. However, this is one of the better spots to see, on occasion, both green and hawksbill turtles.