Hin Bai (Sail Rock)

Koh Phangan · Gulf of Thailand · Thailand

Hin Bai, known internationally as Sail Rock, is a massive granite pinnacle that breaks the surface of the Gulf of Thailand roughly midway between Koh Phangan and Koh Tao. The rock rises from a depth of over forty meters to a peak that stands several meters above the waves, its underwater flanks covered in marine life and hosting the Gulf's most famous dive feature: a vertical chimney that penetrates the entire rock formation, large enough for divers to swim through from bottom to top. The boat ride from Koh Phangan took seventy minutes across flat, warm Gulf water, the rock appearing as a dark tooth on the horizon long before we arrived. Gearing up with the other divers, anticipation was palpable -- Sail Rock's reputation as the Gulf of Thailand's best dive site is well established, and the possibility of whale sharks had everyone scanning the surface for shadows. I dropped in on the rock's eastern face and descended along the granite wall, which was covered in a thick carpet of anemones, soft corals, and encrusting organisms that gave it a fuzzy, organic texture. Schools of yellowtail fusiliers parted around me as I descended, their streamlined silver bodies catching the filtered sunlight. At twelve meters, an enormous giant grouper held station in a recess in the rock, its mouth opening and closing slowly, its eyes following me with the resigned patience of an animal that has watched thousands of divers pass by. The chimney entrance appeared at eighteen meters on the rock's southern face, a dark opening in the granite roughly two meters in diameter. I entered and began a slow ascent through the vertical tunnel, the walls close but not claustrophobic, covered in cup corals and small tunicates. Looking up, the chimney narrowed slightly before opening to a bright circle of surface light at six meters. Emerging from the top felt like being born from the rock itself, a moment of exhilarating transition from enclosed space to open water.