Photoshop magic:

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This photo is from a rebreather dive Glenn Reynolds and I did in 2006, off Cobalt Coast in Grand Cayman. Glenn's wrote and videoed about it in Popular Mechanics. Guess who the photographer/videographer was? The intrepid diver is Nat Robb of InDepth Watersports in Grand Cayman. To learn how to do it yourself, see this YouTube video.