The Red Sea is one of the world’s premiere locations for diving. Major resorts such as Sharm el-Sheikh, Eilat, Aqaba, and El Gouna play host to hundreds of thousands of visitors each year who come to sample a portion of the 2 000 km (1 240 mi) of coral reefs along the Red Sea shores and swim alongside the incredible array of marine life that dwells within. On the east coast of the Sinai Peninsula lies the burgeoning Egyptian resort town of Dahab, itself home to over 50 diving sites (and an even larger number of outfitters). Perhaps the most famous of those diving sites is a submarine sinkhole (or ‘blue hole‘) known simply as the Blue Hole, located at the end of the road just a few kilometres north of Dahab.
Source: M. Kieffer, http://www.flickr.com/photos/mattkieffer/2349924992/. Licensed under the Creative Commons Attribution-Share Alike 2.0 Generic licence.
Source: mindgrow, http://www.flickr.com/photos/28686493@N08/8199787788/ and http://www.flickr.com/photos/28686493@N08/8198702689/. Licensed under the Creative Commons Attribution-Share Alike 2.0 Generic licence.
At the beginning of the above video, you may have noticed a cliff wall lined with 14 embedded memorial plaques. Dahab’s Blue Hole isn’t just one of the Red Sea’s most popular dive sites; it’s also the sea’s most dangerous dive site and perhaps the deadliest major dive site in the world. At least 130 divers have drowned within the Hole’s confines since 1997 (Warning: some may find the embedded video disturbing.).
The same topography that makes the Blue Hole so attractive to divers also makes it extremely dangerous to pass through the Hole into the open sea without advanced scuba equipment. Like other blue holes, the Dahab Blue Hole is a relic of limestone erosion from the last ice age, when sea levels here were lower. Essentially, it’s a vertical karst cave that has been submerged under water. At the northeast edge of the reef surrounding the Blue Hole, there exists a 26 m (85 ft) long tunnel known as The Arch which connects the Blue Hole to the open sea. While the surface of the Blue Hole is safe, amateur divers often attempt to navigate through the tunnel to reach the sea instead of swimming up and over the far shallower portion of the reef known as The Saddle to the south.
A schematic of the Blue Hole. Source: Usellermann, http://commons.wikimedia.org/wiki/File:Blue_Hole_map.png. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported licence.
A technical diver swimming through The Arch’s tunnel. Source: T. Salminen, http://en.wikipedia.org/wiki/File:Dahab_Blue_Hole_Arc_2009.jpg. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported licence.
The major issue with The Arch is its depth. When diving in saltwater below the 33 m (100 ft) mark, divers without professional equipment are likely to experience a condition known as nitrogen narcosis. As gaseous nitrogen permeates into the body and enters the brain under higher partial pressures, complex reasoning and manual dexterity are adversely affected. Emotions also become heightened. Some divers feel intense euphoria and continue to dive deeper, thinking everything is alright; others panic and attempt to ascend too quickly, resulting in decompression sickness as dissolved gases in the body, such as nitrogen, exit the body too quickly (‘the bends’). Even oxygen from the diver’s own airtank will begin to adversely affect the body beyond certain depths due to pressure. The Arch lies 56 m (184 ft) below the surface, well into the narcosis zone and less then halfway down the wall of the Blue Hole (the Hole itself is 120 m, or 394 ft, deep).
Just finding The Arch is difficult enough because of the darkness at these depths. Divers who reach The Arch often misjudge the roof of the tunnel due to light refraction and thus must dive down even farther to properly enter the tunnel (in turn forcing the divers to consume more from their airtank in addition to the heightened threat of narcosis). Strong downward currents exist at the end of The Arch (below the tunnel, The Arch drops off directly down to the sea floor), as well as inward-flowing currents that move against the diver.
Compared to other Red Sea dive sites, the Blue Hole doesn’t have the best scenery or the most fish, as this Spiegel article points out (a recommended read, the article features an interview with Tarek Omar, the poor chap responsible for retrieving bodies off the Blue Hole’s floor). Divers are now attracted to the Blue Hole precisely because of its dangerous reputation. Sadly, because of its increasing popularity, you can probably expect the number of lives claimed by the Blue Hole to continue to grow.
Campbell, E.S. (1997). Decompression Illness in Sports Divers: Part I. Medscape Orthopaedics & Sports Medicine eJournal 1(5). Available at http://www.scuba-doc.com/dcsprbs.html#DCSPartI. Accessed 20 July 2013.
Dive Site Directory (2009). Scuba Diving in the Red Sea: Dive Site: The Blue Hole / the Bells. Available at http://www.divesitedirectory.co.uk/dive_site_red_sea_dahab_reef_the_blue_hole.html. Accessed 20 July 2013.
Gibb, N.L. (2013). Nitrogen Narcosis and Scuba Diving Part I – What Is Narcosis, How Does It Feel? About.com: Scuba Diving. Available at http://scuba.about.com/od/divemedicinesafety/p/Nitrogen-Narcosis-And-Scuba-Diving-What-Is-Narcosis-And-How-Does-It-Feel.htm. Accessed 20 July 2013.
Grossekathöfer, M. (2012). The Bone Garden: A Visit to the World’s Deadliest Dive Site. Spiegel Online International, 13 July 2012. Available at http://www.spiegel.de/international/zeitgeist/the-blue-hole-in-the-red-sea-is-the-deadliest-dive-site-in-the-world-a-844099.html. Accessed 20 July 2013.
Salama, A. (2006). Dahab’s Blue Hole; The Arch. ScubaBoard, 7 February 2006. Available at http://www.scubaboard.com/forums/red-sea/128730-dahabs-blue-hole%3B-arch.html. Accessed 20 July 2013.