Underwater tunnels through aquariums are so common these days that I'm actually disappointed when visiting an aquarium that does not have such a spectacular viewing area that goes through a massive tank. Such massive acrylic windows are costly, but they are enormously popular with visitors.
Sure, just wanted to stress this one was very dim. I imagine that was in part to help conceal the very plain interior walls of the tank, as well as make it "spooky". I've personally always found such tunnels to be inferior to large, flat viewing due to the headache-inducing distortions of the curved acrylic and the often overpowering glares and reflections associated with it.
