Hello Mark,
First the key thing with the Mini II is to be minful of the distance you are away from your subject and what setting you have the lens set at. Witht he focus lever set to Landscape, the camera will be in focus from 4ft to infinity. With it set to close-up, it will focus between 2-4ft.
As for the color on the shots it would be best if you could send me some pics so I can dig into the data on the image to check tthe settings.
I think you have been by our offices before, am I right? If so, we can set a time for you to come in and I can run you thriough the camera if you'd like.
As for all the comments about a light/strobe, most definitely this would help as it woudl help the camera by allowing a higher shutter speed to stop any motion blur as well as bringing in more color to our lovely Jersey water!
Cheers,
Joe