To receive a weekly digest of the best opinions of the week for free, sign up for our Voices Dispatches email. Oceanographers have recently confirmed that the Taam Ja’ Blue Hole in Mexico’s Chetumal Bay is the world’s deepest underwater sinkhole. The hole, which is located near the Chicxulub crater where a dinosaur-killing asteroid struck 66 million years ago, has been measured to be at least 420m deep, surpassing the Dragon Hole in the South China Sea, which is around 300m deep.

Blue holes are formed when water seeps through cracks in the seafloor, dissolving minerals and creating sinkholes. The Taam Ja’ Blue Hole was initially believed to be only 275m deep when discovered in 2021, but a more intensive study revealed its true depth. Researchers used new technology to measure the depth by anchoring a vessel near the hole and dropping a line in. They also dove in with instruments to profile the water’s conductivity, temperature, and depth.

The researchers found that the pit is at least 420m deep, but it could be even deeper. The water in the hole has layers of varying temperature and salinity, with one layer at around 400m deep having values similar to those of nearby Caribbean Sea. This suggests that there may be an underwater seabed connecting the two seas.

The discovery of this unique feature has sparked curiosity among researchers about what lies at its bottom. While there is still much unknown about this mysterious abyss, it is clear that there may be a unique biodiversity within its depths waiting to be explored and linked to physicochemical and geomorphological processes.