This term has other meanings, see Blue hole (values).
Blue hole (from the English. Blue Hole is an underwater vertical cave near Dahab in Egypt.
It is surrounded by coral reefs karst sinkhole depth of about 130 meters. From a depth of 52-55 meters, the cave is connected to the sea by a passage. Overhanging over the passage corals formed a kind of arch, hence the name of the Arch.
The traditional route for Amateur divers consists of diving through the Bells (200 m North of the Blue hole), moving along the reef wall and entering the Blue hole through the upper isthmus called the Saddle of the Arch (at a depth of 6-7 meters). Continue reading