The Blue Hole is a diving location on the southeast Sinai, a few kilometres north of Dahab, Egypt on the coast of the Red Sea.
The Blue Hole is a submarine sinkhole, with a maximum depth within the hole of just over 100 m (328 feet). There is a shallow opening to the sea around 6 m (20 feet) deep, known as “the saddle”, and a 26 m (85 feet) long tunnel, known as “the Arch”, whose ceiling is at a depth of 55 m (181 feet) and whose bottom falls away as it reaches the seaward side to about 120 m (394 feet). On the seaward side the floor drops steeply to over 1,000 metres (3,300 ft). The hole and the surrounding area have an abundance of coral and reef fish. The Blue Hole is popular for free-diving because of the depth directly accessible from shore and the lack of current.
The dive site is reputed to have the most diver fatalities in the world with estimates of between 130 and 200 fatalities in recent years. The reasons for why this site has such a high number of fatalities are not clearly understood.