Blue Hole is a diving location on east Sinai, a few kilometres north of Dahab, Egypt on the coast of the Red Sea. The Blue Hole is a submarine sinkhole (a kind of cave), around 130 m deep. There is a shallow opening around 6 m deep, known as 'the saddle', opening out to the sea, and a 26 m long tunnel, known as the arch, the top of which lies at a depth of 56 m. The hole...