Explained by scientists

"Preserved from the disturbance of time, and isolated in the darkness, the hole holds clues to a very natural part of our planetís life cycle. Itís these terraces and stalactites we set out to map," Erika Bergman, chief submarine pilot on the recent expedition, explained in a recent blog post.

One of the biggest findings of the trip was the discovery of "mysterious tracks" in the sand roughly 350 feet below the surface.

In an interview with CNN Travel, Bergman said the "unidentifiable" tracks remain "open to interpretation."

Bergman, however, wrote in a blog post that they were located near an area researchers labeled the "Conch Graveyard," where they witnessed hundreds of dead conch that likely suffocated after becoming trapped in the oxygen-deprived base of the Blue Hole.

"Presumably, unsuspecting conchs (or other conch shell inhabitants) have been going just a little too close to the edge and falling into the hole at this entrance by the thousands. We can see each conch with little tracks back up the hill trying to escape, then a slide mark where it slid back down after presumably being asphyxiated in the anoxic environment," Bergman explained.

Roughly 300 feet below sea level, Bergman said the crew detected toxic hydrogen sulfide gas.

"There is no circulation in or out of the hole, and our onboard CTD and dissolved oxygen sensor revealed what we had predicted, the bottom is completely anoxic. Thereís not a drop of oxygen below the H2S layer," Bergman described, noting that sargassum seaweed could be a contributing factor.

"The real monsters facing the ocean are climate change and plastic," Branson said, according to Newsweek. "Sadly, we saw plastic bottles at the bottom of the hole, which is a real scourge of the ocean. Weíve all got to get rid of single-use plastic.Ē

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