Blue Hole

The Blue Hole is a diving location on the southeast Sinai, a few kilometres north of Dahab, Egypt on the coast of the Gulf of Aqaba within the Red Sea. The Blue Hole is a blue hole, with a maximum depth within the hole of just over 100 m (330 ft). There is a shallow opening to the sea around 6 m (20 ft) deep, known as "the saddle", and a 26 m (85 ft) long tunnel, known as "the Arch", whose ceiling is at a depth of 55 m (180 ft) and whose bottom falls away as it reaches the seaward side to about 120 m (390 ft). 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.

This description is the opening of the Wikipedia article Blue Hole (Red Sea), by its contributors, reused here under CC BY-SA 4.0 — which means you may reuse it from here on the same terms.