Blue Hole (Orote Peninsula) – Apra Harbor

Site Overview

The Blue Hole on the Orote Peninsula is Guam's most iconic natural dive site and one of the most spectacular geological formations in the western Pacific. This perfectly cylindrical sinkhole begins at approximately 18 metres and drops vertically to depths exceeding 60 metres, creating a dramatic underwater cathedral of clear blue water and ancient limestone. The shaft is filled with crystal-clear water and swirling schools of glassfish that catch the light filtering from above, creating an ethereal atmosphere. The walls are encrusted with sponges, soft corals, and delicate gorgonians, while the deeper recesses host nudibranchs, lobsters, and other cave-dwelling species. At approximately 30 metres, an exit window opens onto the sheer outer wall of the Orote Peninsula, where reef sharks, eagle rays, and pelagic fish patrol the drop-off. This transition from the enclosed shaft to the open ocean wall is one of the most dramatic moments in recreational diving. The site is accessible only by boat and requires Advanced Open Water certification due to the depth and overhead environment. The Blue Hole represents a geological phenomenon formed by the dissolution of limestone over millennia, creating a natural wonder that draws divers from around the world. The geological formation process that created this sinkhole involved thousands of years of limestone dissolution, resulting in the remarkably smooth and vertical walls that define the shaft today.