Most underwater images are post-processed to look pleasing to human viewers. This often results in unrealistically saturated colors. Images taken for the purpose of studying color-sensitive topics such as marine animal coloration, must represent colors as accurately as possible and should not be arbitrarily enhanced. This first requires a transformation of colors from the camera color space to a device independent space. In this paper we present a method for transforming raw camera-RGB colors to a device independent space, optimizing this transformation for a particular underwater habitat. We have conducted an extensive study of the variation of color appearance underwater at a dive site in the Aegean Sea by taking 21 sets of spectrometry and irradiance readings with corresponding photographs of four different color standards. Spectral and photographic data were collected in the presence of natural daylight at various depths and under different weather conditions. In addition to the color charts, we have built a habitat chart to optimize this camera-specific transformation for a given dive site.