National Geographic : 1952 Oct
467 Ektachromles by Jacques-Yves (ousteau Same Reef, 110 Feet Deeper, Reveals Hues Which Only a Powerful Flash Can Illuminate For marine biologists, one advantage of diving in the Red Sea was that water below 20 feet was virtually im mobile, with no perceptible motion from surface waves. Aqualungers at this level detected wave action only by an increase in pressure as surface water rose and fell. Until photoflash went off in front of this sea wall, divers could dimly glimpse only dark blues and greens. Reds and russets were completely absorbed.