I've got photos of a fish just under the water : so, too much blue, not suficiently crisp images of the fish
http://www.geekzone.fr/ipb/topic/46629-retouche-photo-sous-marine/
http://docs.gimp.org/fr/gimp-imaging-photos.html
http://www.gimpons.net/effets-photo.html
http://www.photo-evasion.com/articles/rubrique-infographie-retouche_photo_gimp-1.html