The blue hole is a large ocean cave or pit formed by carbonate sediments found in river sands or islands. Blue holes are usually made up of waves of pure water, the sea, or a mixture of both. Examples include the South China Sea-Dragon Hole, Belize, the Bahamas, Guam, Australia-Great Barrier Reef and Egypt-Red Sea.
The blue hole formed during the last winter which is 2 million years ago. The current sea level was 100 to 120 meters lower than the current sea level. Then the soil was eroded by the erosion caused by the rains and the chemical footsteps, but these were submerged at the end of the ice age.
There were many types of fossils in the blue hole through which the possibility of many creatures living in the blue hole is found. Other life forms found here include marine life and marine fossils, as well as crocodile and turtle fossils found in blue holes. This place was famous by Jacques Courteau who said it was one of the top five scuba diving sites in the world. He brought a ship in 1971 named Calypso to the hole to make a note on its depths.
From the investigations the holes origin is a typical karst lime stone formation which is formed stages leaving ledges at the depth of 21m, 49m and 91m. The great blue hole initially measured depth was 215m and as expedition by the Cambrian measured it’s hole depth as 124m, this differences in measurement is because of the ongoing sedimentation in measurements.
Two submarines in 2018, December descended into the blue hole which is to map it’s interior and the team was able to complete a 3-D map of 1000 foot wide hole using Sonar scanning. They discovered many things and one among them was a layer of hydrogen sulfide at a depth of 300 feet approximately. The water is at that depth blow is dark and lacking of life.