Canon powershot pro 1

I was wondering if anyone has used a Canon Pro 1 underwater. It seems the ikelite housing is about the best option (as there only seems to be 2 housings available period). Since the ikelite will not allow the incamera flash to function are you able to shoot with ISO 50 or do you need to boost it up to get a good exposure without flash.

I was really wanted to find a case that can use my ttl flash metering in camera and the ikelite flashes require the manual controler. How hard is it to set the flash underwater and do the fish actually stick around after you blind them once if you dont have the level adjusted correctly?