to be less than 10 m long but has been measured as 26 m. Moreover, there is frequently a current flowing inward through the arch into the Blue Hole, increasing the time it takes to swim through and increasing gas consumption. Depth and the time taken to find and navigate the tunnel inevitably makes this a decompression dive requiring decompression stops on ascent in order to avoid decompression sickness (DCS). Also, the rate of diving gas consumption increases with depth and effort, which can lead to divers running out of gas or beginning the ascent with insufficient gas to make the decompression stops required. The likelihood of nitrogen narcosis causing confusion leading to poor judgement in an already demanding situation is significant at this depth. Although the effects of nitrogen narcosis may be mitigated by using trimix or heliox the Arch is insufficiently deep to make its use obligatory. Temptation to dive on a single gas tank. The Arch has been dived on single, 11-litre tanks multiple times, but this is dangerously close to the minimum gas requirement for the dive and depends on a fit and relaxed diver with a low gas consumption rate committing no errors or hesitations during the dive. Diving the Arch without a stage tank and without adequate gas planning has resulted in drowning or DCS. Death of Yuri Lipski A notable death was that of Yuri Lipski, a 22-year-old Russian diving instructor on 28 April 2000 at a depth of 115 metres after an uncontrolled descent. Lipski carried a video camera, which filmed his death. This has made it the best known death at the site and one of the best known diving deaths in the world. The video shows Lipski in an involuntary and uncontrolled descent, eventually landing on the sea floor at 115 metres where he panics, removes his regulator and tries to fill his buoyancy compensator but is unable to rise. At 115 m he would have been subject to severe nitrogen narcosis, which may have impaired his judgement, induced hallucinations and caused panic and confusion. Lipski had a single tank assumed to be air. Lipski's body was recovered the following day by Tarek Omar, one of the world's foremost deep-water divers, at the request of Lipski's mother. Omar had earlier twice warned Lipski against attempting the dive. On the bottom, Omar found Lipski's helmet camera, still intact. The video it