(CNN) — Virgin billionaire Richard Branson joined a new mission to solve one of the most captivating mysteries of the ocean -- what lies at the bottom of the Great Blue Hole in Belize?
The Great Blue Hole in Belize is the largest sinkhole in the world -- a giant cavern measuring 300 meters (984 feet) across and around 125 meters deep.
In 1971, underwater explorer Jacques Cousteau put the Blue Hole on the map when he first explored its depths.
Nearly half a century later, despite becoming a scuba hotspot, the Blue Hole's exact features remain mostly unknown. But Cousteau's grandson, Fabien Cousteau, is on the case.
He joined up with Branson -- who runs Ocean Unite, a leadership initiative that aims to help protect the ocean -- and a team of scientists, explorers and filmmakers from the Aquatica Foundation.
The group took submersibles including a manned Aquatica Stingray 500 to the bottom of the hole to chart what lies deep down below.
The Blue Hole is largely unexplored.
Located roughly 40 miles off the Belize coast, the Blue Hole is thought to have once been a giant cave on dry land, thousands of years ago.
As the ocean rose again, the cave flooded. It's now part of the wider Belize Barrier Reef Reserve System, which is a UNESCO World Heritage Site.
The Blue Hole has never been fully mapped or plotted -- the idea is this new expedition might answer the question of what lies at the bottom of this enigmatic cavern.
Billionaire Richard Branson is going to be traveling to the bottom of the Great Blue Hole.
Vincenzo Lombardo/Getty Images Europe/Getty Images for VIRGIN VOYAGES
One of the submersibles on the expedition had additional lighting to allow both the on board team and the viewer at home to see as much as possible.
There were also two support vessels on site, a luxury charter yacht providing accommodation and amenities for the team and a research vessel to support the expedition.
Following the dive on December 2, vessels will continue to monitor and explore the site for two weeks, collecting data that will allow experts to construct real-life models of the Blue Hole's geography.