I just recieved my C-740 and a PT-018 housing and am going to use them week after next on a Nekton cruise. I also just purchased two sets of PowerEX 2000mah batteries, and I am wondering if anyone can tell me what kind of battery life I can expect while using the camera underwater. I plan to have the monitor on (of course) and the flash setup to fire with every picture, but not the constant AF.