This is, without doubt, the most famous site on Guam and the one everyone wants to visit. Located off Orote Point, which is the southern spur of land at the entrance to Apra Harbour, it is a natural limestone shaft that descends into the reef.
The opening is huge, at a depth of 17m and once inside, the shaft drops to 100m+. The first exit hole is at 40m, so it's vital that you check your descent rate and depth continuously. There is another exit much further down, but only the most experienced will be able to make it to this depth. The whole structure is made up of coral, so fish life is profuse and you can expect to encounter eels, smaller reef fish and naturally a great variety of soft and hard corals. Larger pelagics can be seen in the depths and outside.
Once you've exited, ascend to 25m and follow the reef wall round and up to 17m where the reef becomes flat and you'll come across a myriad of schooling fish that can be fed by hand.
All-in-all, this is a truely breathtaking dive, but it must be emphasised that only advanced divers should enter the hole and even then care must be taken with depth as the shaft will appear bottomless. Less experienced divers will find plenty to interest them around the entrance and surrounding reef.