Hole itself is no more dangerous than any other Red Sea dive site but diving through the Arch, a submerged tunnel, which lies within the Blue Hole site, is an extreme dive that has resulted in many accidents and fatalities. The number of Blue Hole fatalities is not accurately recorded; one source estimates 130 divers died during the fifteen-year period from 1997 to 2012, averaging over eight per year, another claims as many as 200. This includes some snorkelling deaths at the surface unrelated to diving the Arch. The Egyptian Chamber For Diving & Watersports (CDWS) now stations a policeman at the Blue Hole to ensure divers are diving with a certified guide who will make sure safety procedures are followed. The ceiling of the Arch is 55 m (170 ft) deep, which requires suitable training and equipment as 40 metres is generally considered the limit for recreational diving. The Arch presents little problem for suitably equipped and competent technical divers. The main challenge is gas management because any delays or errors at this depth, plus the time to negotiate the horizontal section, will need more than a single tank of breathing gas to do safely. If gas is not carefully planned the diver may lack sufficient gas for the decompression stops or run out of gas altogether. The main reasons suggested for the accident rate include that the: Notoriety of the site attracts divers and presents a challenge that tempts many who lack the necessary competence. Accessibility of the site and the clear, warm waters of the Red Sea makes the dive look more benign than it is. At over 55 m, and with an overhead environment, the dive requires competence usually associated with moderately advanced technical certification, with a technical extended range (55 meters on air) or Tech 60 (normoxic trimix) as a minimum qualification. The entry to the Arch is not easy to find because of the indirect line between the Blue Hole and open water. Divers who miss the entry may inadvertently continue to descend past it, while the floor continues on down to well over 100 m providing no visual depth reference. Time taken to pass through the Arch may be underestimated. The tunnel appears shorter than it actually is because of the clarity of the water, the light at the outside end and the lack of reference points; divers report that the tunnel appears