The Bells is a beautiful spot near the “Blue Hole” in Dahab, Egypt. The entry of the small arch is at 20m and the exit at 25-28m. It’s almost like low-level flying when you’re going down there. To reach the spot, just walk by all the restaurants @ Blue Hole, pass the memorial stones and then you’ll see the entry just below. Before diving, make sure no scuba diver is blocking the hole (they tend to stay in there forever :) )
My dive was pretty quick since I really like the “almost flying” sensation.
Here is a video I made during my stay in November 2011.