Recently, scuba divers have found what appears to be a river at the bottom of a quarry.

Wait, what?

I know; it’s kind of hard to wrap your head around. Cenote Angelita is a cenote in the Yucatan Peninsula in Mexico. A cenote is “a deep sinkhole formed from the collapse of limestone bedrock that exposes groundwater underneath.” According to Ripley’s. Cenotes often have a vast majority of underwater caves, as well. When first looking at Angelita, it looks like any other natural swimming area; clear, fresh water. It isn’t until about 29 meters under the water where the real magic happens. Under the fresh water is a one-meter thick layer of hydrogen sulfide, which is heavier than the fresh water above. Underneath the hydrogen sulfide is the ever denser saltwater. Looking at the divide in the water is absolutely breath taking. If it weren’t for the presence of the diver in the photos, I would not have even known the picture was taken under water; it looks like a regular river. This phenomenon is called halocline. Halocline happens when cold, dense seawater sees a very sharp desalination gradient. This also explains how we see ice in the ocean, since we know saltwater doesn’t freeze. This process occurs when the untouched saltwater in the underlying caves of Angelita meets the fresh rainwater when it rains. So far, Angelita is the only place where this amazing site is possible to be seen. There are plenty of other cenotes in the Yucatan, which is a popular tourist spot in Mexico. Tourists can visit the caves and see the mysterious salt and fresh water in the different caves.

One very interesting thing is that much like when you shake an oil and vinegar container, when someone passes through the halocline, the layers mix. Eventually, the layers separate again, and the halocline is once again formed. The sole thing I take away from this: Goo Lagoon from SpongeBob SquarePants IS indeed possible.

Sources:

http://www.ripleys.com/blog/mysterious-underwater-river/

https://en.wikipedia.org/wiki/Halocline