OK...
Open the image in PS and use the "magic pen" to select the tones that correspond to the diver: use only, say, a range of 5/255 tones, and select several times in "additive" mode until you have a selection that includes the diver and nothing else (this is sometimes a bit fiddly). Then make this a new adjustment layer, and try different combinations of whatever you like, in levels or, better, curves or even contrast.
I find this easier than drawing a freehand marquee around the diver, then playing with the layer created from that because the selection is less precise. If you do just draw a marquee, then save the original image as a snapshot and make this the target for the "history brush". Ensure that the marquee is a bit bigger than the diver. After adjusting the image you can carefully paint back the background with a small diameter history brush. This is much easier with a graphics tablet than a mouse!
These techniques are in several of the PS books, so you can look up the details and other ideas, too.
The best answer, though, is to take a different image with a really wide angle lens and much closer to the diver to avoid what Jim Church called the "blahs".
Tim
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