Something new (for me) to make blending composited images easier.
After I had prepared a preliminary layer mask on the seal layer and added a curves adjustment layer for adjusting the basic colors,
I added a Hue/saturation adjustment layer and desaturated the cyans to minimize the color bleed from the bright water background. Then I paint black on the Hue/Saturation mask to limit the desaturation to the transition area of the seal near the edge of the mask
This helps eliminate the "green screen fringe" that is often obvious when pasting a picture that used different lighting.

Forum discussion: http://forums.dpreview.com/forums/read.asp?forum=1006&message=26262758