There are charts out there for exposure adjustment under water, which varies based on depth. The deeper you go, the more you need to compensate. Also, the deeper you go, the more filtration you will need to correct for the filtering nature of water. This is one reason why so many underwater photos use flash - with the flash being essentially on-camera, no color-correcting filter is needed. If you are ever thinking of taking this camera deeper than say 4-5 feet, or have even a vague suspicion you might want to try it some day, get the V. The V has improved water sealing around the door (the IV-a was prone to flooding), and it has a built-in meter that will let you shoot aperture preferred. This is a HUGE help if you're shooting without a flash, because it takes care of calculating the filter factor- just put on the filter you need topside, then get in the water and shoot.