Color correction filters are absolutely necessary for correct and vibrant colors in underwater video unless you are shooting either macro, at night, or in dark or murky water, all while using lights. The reason for manual white balancing is to tell the camera what is the value of white. Camera sensors do not see color, they only see the lumiance values of black to white, through either a Beyer Filter (1-chip), or through three discrete sensors (3-chip) each seeing only the red, blue or green parts of the image separated by a prism. The value of white varies dependant on depth, visability, distance, angle, color temperature of the light source, and other factors. Once the camera knows what is white, it will then be able to calculate accurate values for all of the colors. Color correction filters work by blocking a percentage of the short wavelength light (mostly blue then green) and allow the longer wavelength light (red then orange) to pass through. The deeper you go, the less color corrected light that your camera will see, so low lux performance is very important, especially the deeper you go. I shoot with a Sony FX1 in a Bluefin HD housing, and always shoot with a color correction filter during the day, and get outstanding color in my videos. I use lights only at night, or if in a dark overhead environment. Nothing beats the natural light of the sun, manually white balanced through a color correction filter for underwater video. Also, it is usually necessary to manually white balance often, due to changing conditions and depths
