Blue Hole

The Blue Hole is a submarine sinkhole located in Dahab, Egypt, on the Red Sea coast, sitting literally at the water's edge — roughly 10 metres from shore. The circular hole measures about 70 metres wide within the reef table and drops vertically to around 90–95 metres, with the sinkhole bottom recorded at approximately 94–95 metres depth. A colourful shallow coral saddle links the hole to the open sea, and embankments of hard and soft coral slope gently down into it. The site attracts scuba divers and freedivers from around the world, with national and international freediving records set here owing to the excellent conditions and extreme depth.

The defining feature for technical scuba divers is the Arch — a 27-metre-long underwater tunnel at 55 metres depth that connects the inside of the hole to the open sea, offering remarkable light effects. Diving to the sinkhole bottom at around 94–95 metres requires TDI Advanced Trimix or GUE Tech 2/3 certification. The Arch dive itself demands TDI Extended Range or GUE Tech 2 qualification, as it involves a long decompression profile with multiple gas mixes. These are overhead-environment dives at extreme depth, well beyond recreational limits; exceeding those limits has caused fatalities at this site.

Marine life in and around the Blue Hole includes reef fish, pelagic fish, turtles, rays, and occasional sharks, though sharks are considered rare in this part of the Red Sea. The reef structure supports hard and soft corals along the sloping embankments of the saddle area, making shallower sections appealing even outside the technical context.