And some disappointing information from Inon. Does anyone have any direct experience with the G9 and W/A glass...
"...The Canon G9 is a great digicam however, with its extra wide zoom range (35mm-210mm), wide angle conversion lenses are not practical. This is because the master lens on the G9 (as in all digicams) needs to be set at it’s widest zoom setting to achieve optimum imaging. If the G9 is set at it’s widest zoom setting, the conversion lens will vignette (be seen in the image). If you zoom in to eliminate the vignetting, the master lens has to physically travel a significant distance. In doing so, there will be no benefit in using a wide angle conversion lens because the underwater angle of coverage will not be much different that shooting the G9 at it’s widest setting using no wide angle conversion lens.
With all this said, the G9 Ikelite housing does have a 67mm threaded port and Ikelite does have an AD bayonet adapter for INON lenses however, there is just no wide angle advantage with this camera/housing combination in attaching said lenses. Please let me know if you have any other questions."