Blue Hole, Submarine sinkhole in South Sinai Governorate, Egypt.

The Blue Hole is a circular underwater opening along the Red Sea coast that drops away from a shallow entry point. A tunnel connects the inner chamber to the open ocean and runs beneath the reef edge.

Bedouin tribes of the area avoided the hole before the 1967 Six-Day War, when Israel occupied Sinai. In 1968 a group led by Alex Shell made the first scuba dive here and noticed the underwater arch; the site's reputation grew until Sinai returned to Egypt in 1979 under the peace treaty.

The shore above the hole is largely Bedouin-run: multi-storey café terraces and souvenir shops belong to families of the partly nomadic tribes of the Sinai desert. A memorial to divers who died in the hole stands on the bank, though name plaques were stopped because they deterred tourists. Freedivers including Natalia Molchanova, the first woman to pass the Arch on one breath in 2005, made the site a landmark of the sport.

Several dive centers nearby offer trips for beginners and experienced divers with separate entry points depending on skill. The shallow area works for snorkeling while deeper dives require preparation and guidance.

On the seaward side the wall drops away beyond 1000 meters and forms a dark blue backdrop behind the coral. Schools of small fish move along this edge while larger species emerge from the depth below.