Largest ever 'blue hole' uncovered 1,300 feet deep in the sea and scientists still haven't reached the bottom

Scientists believe they now know just how deep a particular blue hole goes, and have proclaimed it may be the largest in the world.

The ocean is a fascinating place, and what we know about it is always changing.

Just outside the Yucatan Peninsula, near Mexico and Belize, scientists believe they have located the 'deepest known blue hole' in the world.

It is estimated to measure at least 1,380 feet below sea level. So, as you can imagine, it has piqued the interest of anyone with a desire to know more about the very deepest and darkest ocean depths.

To top it all off, scientists haven't even reached the very bottom of it yet.

Discussed in a research paper published in the journal Frontiers in Marine Science, researchers have detailed the huge expanse and what it could mean for future studies of underwater life and how 'blue holes' are formed.

Scientists aren't sure they've even reached the bottom of the world's largest 'blue hole' yet. (Joan A. Sánchez-Sánchez)

These 'blue holes' are actually marine caves, believed to have been formed and carved over thousands of years by glacial runoff during the Ice Age.

Typically measuring hundreds of metres below the ocean's surface, they present a fascinating study, and so far, many divers and marine explorers have failed to reach the very bottom to see what happens at the base of them.

Limited oxygen can be one of the biggest concerns for those keen to dive in and see what's in them, and some of these marine caves can be home to the gas hydrogen sulfide, making it toxic to be diving without the right training and equipment.

Initially, the largest 'blue hole' - known as Taam Ja’ Blue Hole (TJBH) - was thought to only measure 900 feet down, but in December last year, it was calculated to be even deeper and stretch further towards the ocean floor.

The Taam Ja’ Blue Hole measures over 1,300 feet. (Frontiers in Marine Science)

The previous incorrect measurements were thought to be down to limitations in the echo-sounder technology, which uses sound waves to determine depth and calculate how far down the hole stretches.

This time, to get the right measurements, or at least get a more accurate view until they can finally reach the bottom, the science team used a conductivity, temperature, and depth (CTD) profile which means they were able to get a better understanding of how far and how deep it reaches.

While they haven't reached the bottom yet, the CTD profile did stop at at 1,380 feet, but can technically stretch to 1,640 feet, so whether or not it did touch the bottom or simply was blocked is something the scientists are also still confirming.

Another interesting finding was that a layer of water below the 1,312 mark resembled the Caribbean Sea, hinting that there could be links between some of these underwater marine caves but more research will be needed.

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