I'm assuming that you're just using the G9 in Canon housing with nothing else. Given the limitations in your setup, this is a really good shot. Its in focus, pretty well composed, good depth of field, and you go the whole fish in the shot.
My only real comment on how to improve this shot using the same equipment you have: get closer to your subject. This will cut out some of the blue, but not all of it. It will also make your subject much bigger in the frame and give it more presence.
If you don't want to sink a lot of money into a lighting setup, you can take a look at Magic Filters. They'll add in some of the color and take out the blue cast. Using them takes a bit of learning, but its much cheaper than a strobe or two. You can find more information about them
here.
Cheers,
Ken