The famed Belize Blue Hole lies some 30 miles offshore from Belize City on Lighthouse Reef, part of the great Belize Barrier Reef system, the world's second-largest.
Although it was made famous in the mid-Twentieth Century by filmmaker Jaques Cousteau, it has been around for a very long time - millions of years, in fact.
The Belize Blue Hole is a collapsed cave or sinkhole, almost perfectly round in shape, that formed during the last Ice Age. As the Ice Age ended, global temperatures rose, the vast glaciers melted and sea levels rose, submerging the sinkhole under the sea. Gradually coral reefs systems grew around the circular edge. Its depth has been measured at 124 meters (or 407 feet).
Stalactites are found at the bottom of the hole, confirming its formation eons ago above the sea surface.
Today, the Belize Blue Hole has become an icon for the tiny nation. It adorns most tourism literature, posters and ads, becoming synonymous with Belize. It is a mecca for divers and snorkelers alike and a few resorts and dive operators offer day-long dive trips to the hole, among them Blackbird Caye Resort and Turneffe Island Resort.
Divers who want to go all the way to the floor of the Belize Blue Hole should have advanced open-water certification, due to its depth. The floor is comprised mostly of coral sand, and although not many fish are found in its somewhat sterile, crystal-clear depths, one can usually find a variety of sharks in the crevices near the bottom. Common are nurse sharks, Caribbean reef sharks and black-tipped sharks, often found dozing in the cool depths. Giant Nassau grouper are fairly common here as well.
Snorkelers shouldn't feel left out, however. The reefs around the lip of the hole are excellent snorkeling areas - the water is shallow, clear and filled with colorful reef fish.
The Belize Blue Hole is a protected area of the Belizean marine reserve system.