Jacques Cousteau's Grandson to Map Depths of Massive Blue Hole Off Belize's Coast
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A new expedition is set to map the bowels of a mysterious blue sinkhole off the coast of Belize, made famous by explorer and filmmaker Jacques Cousteau, who was so impressed with the formation he named it one of the top scuba-diving sites in the world.

Cousteau visited the sinkhole in 1971; and now nearly a half a century later, his grandson Fabien Cousteau, also a filmmaker and ocean conservationist, will return to Belize's submerged Great Blue Hole, which is so big that two Boeing 747s could hide out comfortably in its innards, according to a statement.

For the expedition, Cousteau has teamed up with project lead Aquatica Submarines, a submersible company; the Roatan Institute of Deep Sea Exploration; and entrepreneur Richard Branson, as founder of Virgin Group and co-founder of Ocean Unite. [In Photos: Stunning Sinkholes]

The Blue Hole, part of the Belize Barrier Reef Reserve System, a UNESCO World Heritage site, is 1,043 feet (318 meters) in diameter and 407 feet (124 m) deep.

The eerily beautiful hole lies at the center of Lighthouse Reef; it wasn't always a sinkhole, but rather started as a limestone cave formed during the last glacial period, according to Atlas Obscura. But with rising oceans, the cave flooded and collapsed, leaving behind mesmerizing geological formations below the water, enticing divers to flood in from around the world.

Under the blue depths, divers can see, for example, large stalactites — formations that hang like icicles from the limestone ceiling — and stalagmites — which are rock formations that rise from the sinkhole floor, according to Atlas Obscura.

The team will make multiple dives to the bottom of the Great Blue Hole with piloted submersibles to collect scientific samples, map out the structure of the hole and record such environmental factors as water quality data, which can provide insights into how much light reaches parts of the water and how much bacterial life there is, according to Engadget.

The main goal is to map out the hole's still-mysterious internal structure using sonar, which uses sound waves to detect objects — formations or surfaces — underneath the water.

Further, the team hopes to find an alleged oxygen-depleted layer near the bottom of the Blue Hole. Such an area could offer an opportunity to find preserved life unperturbed by the famous element, the team members told Engadget.

But they also really just want to bring awareness to ocean conservation — such as through shooting a live video from the depths — to educate the public about the threat that such areas face because of the pressure of global warming.

Originally published on Live Science.