From the air it looks like a giant, dark blue spot, in the midst of the turquoise waters of the Caribbean. The “Great Blue Hole” is about 70 kilometers from Belize City. The unique phenomenon, which stands out from the surrounding water due to the difference in water depth, has a diameter of almost 300 meters, is a total of 125 meters deep and has an underground cave system with enormous stalactites. Because of this the area is popular with divers and snorkelers.
What is the Great Blue Hole?
The Blue Hole was formed tens of thousands of years ago, when glacier water flowed through the limestone deposits of the Lighthouse Reef, resulting in huge underground caverns. The roof of one of these caves collapsed during a displacement of the Earth’s crust, leaving the visually stunning spectacle in Belize and its most famous dive site. It is located in the center of the Lighthouse Reef, halfway between Half Moon Caye to the south and the Northern Caye.
The Great Blue Hole of Belize is more than 120 meters deep and more than 300 meters wide from edge to edge. It was made famous by the illustrious Jacque Cousteau and his diving vessel the Calypso in the 1970s. The Great Blue Hole is only accessible by two narrow channels, through the encircling coral reef. The deep blue of the hole can be very imposing, even for the most experienced diver.
The area is protected from fishing as it is the centerpiece of the Blue Hole Natural Monument Marine Parks. The reef around the edge of the hole is just a few feet below the surface and filled with anemones, starlet and club finger corals – an excellent place to snorkel.
Diving in the Great Blue Hole
It is possible to dive all year round at the Lighthouse Reef and the Great Blue Hole, and for the most part the climate is sunny and warm, with July to September being the hottest months. The wet / dry season on the mainland is not really of concern here as it is far off the coast and rains are less frequent than elsewhere in Belize. But sporadically might occur throughout the year nonetheless.
Visibility is generally very good and in the range of 25-40 meters. The stronger winds in March and April can whirl up the sediment and the warmer summer months bring forth plankton and algae. Visibility is reduced to 20 meters at these times. The water temperatures are generally at 29°C, but fall a little to 27°C from November to February.
If you dive the south side, you will approach the shallowest cave systems at about 30 meters. You will notice how the angles of the wall change by an overhang with stalactites, some of which are more than 1 meter in diameter and up to 6 meters in length. Fallen stalactites lie at the bottom of the cave, where stalagmites grow upwards like a series of decaying teeth, as if they complete a grotesque underground shark mouth. Underneath is an entrance to a cave that adds an uncanny feeling to this already atmospheric dive.
The north side is comparable to the south, with stalactite formations at 30-42 meters, but, unlike the southern side, there is no lower bar of the stalagmites here, only the upper “jaw” of stalactites hangs over the sunken karstic precipice. The ground is another 80+ meters below and very little exploration was done there, apparently it is just a large hill of sand and other fallen debris that has accumulated over the years.
The blue hole is part of the Lighthouse Reef of Belize. Just second in size to the Great Barrier Reef in Australia. It stretches over 298 kilometers off the coast and also offers a home to more than 350 species of fish. In 1996 it was named a UNESCO World Heritage site. In 2009, the list was added to the list of endangered World Natural Heritage sites.