If flying over the offshore coast, you’ll easily recognize this large circular formation with its magnificent blue-to-black hues surrounded by neon blue water. Though there are other, smaller, blue holes around Ambergris Caye, Caye Caulker, and elsewhere, this is the Blue Hole to beat them all. The submerged shaft is a karst-eroded sinkhole with depths that exceed 400 feet. In the early 1970s, Jacques Cousteau and his crew explored the tunnels, caverns, and the listing stalactites that were angled by past earthquakes. This twilight world has suspended sediment and little fish life.

Most dive groups descend to a depth of about 135 feet. Technically, this is not a dive for novices or even intermediate divers, though thousands have done it. It requires a rapid descent, a very short period at depth, and a careful ascent. For a group of 10 or more, at least three dive masters should be present. Critics write it off as a “hyped-up macho dive.”

From the standpoint of undersea life, the lip of the crater, down to about 60–80 feet, is a much more interesting dive. Be prepared for some of the largest midnight parrot fish you will see anywhere. Stingrays are also to be found in sandy areas, as are feather duster worms. Angelfish, butterfly fish, and small reef fish cluster around coral heads and outcroppings. Occasional barracudas and small groupers guard their territories.