Deepest blue hole

The deepest blue hole is the Taam Ja’ Blue Hole located in Chetumal Bay off Mexico's Yucatán Peninsula, which descends to at least 420 m (1,377 ft) below sea level. Its depth was logged with a device measuring pressure level by scientists from El Colegio de la Frontera Sur (ECOSUR) in December 2023, with their findings published in Frontiers in Marine Science on 29 April 2024. However, the absolute bottom of this submarine sinkhole has yet to be determined.

This surpasses the previous holder, the 300.89-m-deep (987-ft) Dragon Hole (aka Yongle Blue Hole) and situated off the disputed Paracel/Xisha Islands in the South China Sea.

Its name meaning "Deep Water" in the Mayan language, the Taam Ja’ Blue Hole was originally found by a diver in 2003 but only formally investigated in 2023. Using echo-sounding technology it was determined then to be 274 m (899 ft), which would have made it the second-deepest blue hole globally. However, further study using different measuring techniques revealed that it went considerably deeper than thought, and the final depth is still to be confirmed.

The region is renowned for its erosion-susceptible karst landscape, which has resulted in hundreds of sinkholes both on the seafloor and on land. Terrestrial flooded sinkholes (known as cenotes) are connected by a series of caverns that form the largest underwater cave network: the Sistema Sac Actun ("White Cave System") has been measured to extend for at least 371.958 km (231.12 mi).

Other notable blue holes in the region are the Great Blue Hole, with a depth of 124 m (407 ft), on the Belize Barrier Reef and the Dean's Blue Hole off The Bahamas' Long Island, which at 202 m (663 ft) is the world's third-deepest blue hole currently recorded.