Bajo Alcyone

Puntarenas · Cocos Island · Costa Rica

Bajo Alcyone stands as the most iconic dive site at Cocos Island and the undisputed holy grail of hammerhead shark diving worldwide. This isolated 600-metre-long seamount rises from the deep ocean floor to within 25-30 metres of the surface, approximately 1.5 kilometres off the southern coast of Cocos Island, a UNESCO World Heritage Site located 550 kilometres from the Costa Rican mainland in the eastern Pacific. The experience at Bajo Alcyone is unlike anything else in diving. After descending the mooring line to the seamount's exposed rocky plateau at 30-35 metres, divers hunker down behind boulders and look up. Overhead, the water is thick with scalloped hammerhead sharks, sometimes hundreds strong, their distinctive T-shaped heads and sinuous bodies backlit by the tropical sun filtering through the blue. The sharks use the seamount's upwelling currents and the cleaning services of resident fish to maintain their health, returning day after day in numbers that stagger even veteran divers. Beyond the hammerhead spectacle, Bajo Alcyone attracts an astonishing diversity of pelagic life. Whitetip reef sharks blanket the seamount's rocky surfaces in the dozens, whale sharks cruise through during warm-water months, mantas make regular flyovers, and sailfish have been spotted slicing through schools of baitfish on the edges. Bottlenose dolphins, Galapagos sharks, marbled rays, and green sea turtles are common supporting cast members in this ocean theatre. Diving Bajo Alcyone requires genuine commitment. The 36-hour liveaboard crossing from Puntarenas traverses open Pacific swells, and the seamount itself presents strong, shifting currents that can change direction during a single dive. Depths of 30-35 metres limit bottom time, and the remote location means self-rescue capability is important. Most operators require Advanced Open Water certification and significant open-water experience. The reward, however, is participation in one of nature's most magnificent marine gatherings, a spectacle that Cousteau himself called the most beautiful island in the world above and below the waterline.