Green Rock

Koh Tao · Surat Thani Province · Thailand

Green Rock is a tumbled granite playground off the northwest tip of Koh Nang Yuan. The site takes its name from algae-covered boulders breaking the surface, but the real attraction lies beneath, where boulders continue in a chaotic pile down to 25 metres, creating one of the most topographically interesting dives in the Gulf of Thailand. If you enjoy navigation puzzles and squeezing through gaps that open into hidden chambers, Green Rock delivers dive after dive. The dive begins on the north side, dropping through a canyon between massive boulders into a world of swim-throughs and tunnels. Gaps range from wide corridors to narrow slots requiring careful fin technique. Torchlight reveals giant groupers wedged into corners, moray eels coiled in crevices, and blue-spotted ribbontail rays resting on sandy patches. The interplay of light and shadow as you move between open water and enclosed spaces gives the dive a dynamic, cinematic quality. Turtles are Green Rock's most reliable residents. Hawksbill turtles rest on flatter boulder tops, lifting their heads with mild curiosity as divers pass. Green turtles graze on algae, their powerful jaws scraping the surface with audible crunching. Multiple turtles on a single dive are common, making this one of Koh Tao's best turtle-interaction sites. The deeper slopes from 18 to 25 metres are where sharks appear. Blacktip reef sharks cruise the perimeter in small groups, their dark-tipped fins unmistakable against the sand. Giant groupers hold territory in larger caves, barrel-shaped bodies barely fitting through entrances. Yellowtail barracuda form aggregations above the pinnacle, and banded sea kraits weave through the boulders on hunting forays. Green Rock rewards multiple visits because the maze-like structure means you discover new passages and creatures every time.