Planet Earth has a lot of strange, fascinating things on (and below) its surface. We may not ever understand it completely— though we will most certainly try. It seems that almost every day scientists are making new discoveries about our home, though whether those discoveries answer questions or just present more of them seems to depend on pure luck and happenstance. Recent discoveries about the Great Blue Hole, for example, have only confirmed our planet’s strange and mysterious nature, and, while answering some questions, have also added to the mystery of our little blue planet. 

So, Back Up— What Is The Great Blue Hole?

About 70 kilometers off the coast of Belize, in the middle of the Belize Barrier Reef Reserve System, there’s a rather large…well, hole. It’s not just any hole; it’s a giant, underwater sinkhole. This hole is almost a thousand feet wide and over four hundred feet deep, and it’s the second-largest sinkhole in the world, coming after the Dragon Hole in the South China Sea. What is, perhaps, even stranger, is that this massive hole is almost perfectly circular. 

Where did this giant underwater hole come from, you might ask? Well, sinkholes like these are actually the result of ice ages past. The Great Blue Hole was probably once a series of limestone caves, formed during one of the ‘glacial periods’. As glaciers melted and sea levels rose, the limestone beds collapsed, and the caves were flooded with water—giving us the strange underwater sinkhole that we have today. In a recent expedition to the bottom, scientists discovered that we can still see stalactites lining the walls, just like what we would see if it were still a cave on dry ground. 

It’s A Giant Hole, So What?

Other than the fact that it’s a giant underwater sinkhole (seriously: how cool, and just a little bit freaky, is that?), there are a lot of things that make this an interesting place, and which draw many tourists to the spot every year. The French explorer who first brought it to fame in the 1970s, Jacques Cousteau (no relation to the similarly-named Pink Panther detective), declared it to be one of the best scuba diving sites in the world— and it really is. Even today, divers will come from all over the world to explore it, even if they don’t make it to the bottom. 

If you happen to go scuba-diving in the area, even just around the surrounding reefs, you’ll see a lot of unique marine species, from fish to sharks to conches, and if you venture into the top of the hole itself you’ll probably get to see some of the stalactites from the cave’s pre-ice age days. But this dive isn’t for everyone; you have to be a skilled diver in order to go (according to some sites, meaning you must log at least 24 other dives before being allowed to go scuba-diving here). Some recent discoveries might explain why.

What Did They Find At The Bottom?

While the Great Blue Hole may look like a beautiful thing from the top (which it is), it also presents something a little more sinister the deeper down into it you venture. A recent team which explored the hole (including scientists, filmmakers, and even Fabien Cousteau, the grandson of the Cousteau who first brought fame to the strange sinkhole) made some pretty unsettling discoveries when they took a ship down to the bottom of the hole. Thanks to recent technology, we now have a pretty good 3D map of the entire structure— though maybe it would be better, or certainly less freaky, if we didn’t. 

First of all, the bottom of this hole is poisonous. About two-thirds of the way down, the water is full of hydrogen sulfide, which means there’s no oxygen to be had for any marine creatures unfortunate enough to get stuck at the bottom. Not only is there no oxygen for the creatures, but the hydrogen sulfide itself is extremely toxic and corrosive, which means that the hole kills off anything that happens to get stuck in its base. Explorers from the team stated that there were thousands of remains of marine life, like conches, that, presumably, had fallen in when they got a little too close to the edge. One explorer said that they could actually see the little prints of the conches trying to climb back up and the marks where the conches fell back down because they had been asphyxiated by the toxic water. The hole is basically a marine life graveyard. 

Dark Endings

Marine graveyards, however, are not even the creepiest things that the explorers found waiting for them at the bottom. The team also discovered the bodies of two divers at the bottom of the sinkhole. Three divers have been known to have gone missing after trying to explore the Great Blue Hole, but as of right now, we are not certain who the two divers are that have been discovered, nor is it known exactly how they died. The team of explorers contacted local authorities immediately to let them know that the bodies had been found, but the authorities decided to leave their remains in the hole, stating “they are at peace” where they are. 

The Great Blue Hole may be a beautiful place and a major tourist attraction, but it continues to hold dark secrets and unhappy endings for those who become trapped at its base. Still, however, scientists and explorers will continue to study it, and learn more about it (hopefully from the safety of a ship), searching for answers not only to the Great Blue Hole itself but to our little, big blue planet in general.