The F30 is a great available light camera. It would be an ideal choice for Magic Filters. However it doesn't have full manual control, so it would not be the best choice with a strobe.
The Olympus SP-350 is a great choice. I have a SP-310 (7MP, no hot shoe). Manual control is very easy, with quick exposure compensation. You can shoot RAW and convert to JPEG in-camera. So if you want to make minor white balance changes you don't need a computer.
The new G7 looks nice, but only with the Ikelite housing once it's available. The Canon housing is a joke. No hot shoe and no wide angle lenses with the Canon. Considering the cost of the camera and Ike housing, you might be better of buying a used housing for a D70 or 350D.