Blue Hole

Dahab's famous sinkhole is really two dive sites sharing an address. The one most people do is lovely and undemanding: drop through the Bells chimney, drift south along an outer wall stepped with coral, and glide over the shallow saddle into the sunlit bowl. The other - the Arch, a roughly 26-meter tunnel through the reef wall with its ceiling near 55 meters - belongs to technical diving, and the site's grim reputation was earned almost entirely by people who attempted it without the training, gas, or support it requires. No official count exists; conservative estimates put the deaths well past one hundred, and memorial plaques line the cliff above the entry. Dived within limits, it is a calm, current-free pleasure. The shaft itself bottoms out somewhere between about 92 and 120 meters depending on the survey.

その瞬間のために: The Bells chimney entry; the saddle crossing into blue light; freediving culture at the surface; sobering memorial wall ashore.

地形: A collapsed circular shaft in the fringing reef, its floor far below recreational depths, ringed by living coral walls

エントリー: The classic dive enters at the Bells, a narrow chimney north of the hole, follows the outer wall south, and crosses the saddle at about 7 meters into the hole itself. Proof of certification is checked.

危険生物・リスク: The Arch has killed experienced divers as well as reckless ones - depth, narcosis, and a deceptive exit; freedivers and scuba traffic share the bowl; midday snorkeler crowds.

許可証＆ルール: Protectorate entry fee; guides and proof of certification required, with technical dives subject to additional checks.

保全: Inside the Ras Abu Galum protectorate; entry tickets fund management. The saddle's corals take heavy traffic - keep fins up.

ナイトロックス: ここでは効果的です——このエリアのプロファイルは、ナイトロックスが無減圧潜水時間を有意に延ばせる水深帯にあります（適切なトレーニングを受けていることが前提です）。