Interesting...this was fresh water???
I think that if you adjusted your exposure to provide a darker background, you might have forced the viewers eyes to concentrate more on the subject. I could be biased as where I dive, most of the light in my shots comes strictly from strobes.
Were you using some sort of red filter? There is a definate color cast in your image. I hope you don't mind - I loaded it into photoshop and applied Image>Adjust>Auto Levels, then Edit>Fade Auto Levels and faded by about 12%, then applied a slight crop, and then slightly sharpened the photo under the Filter menu (actually, probably sharpened a little too much).
These options obviously weren't available to you underwater, though I wonder if your white balance setting may have been adjusted to improve on that color cast?
Hope this helps.