and

The in situ estimation of the length of marine biological specimens or features by Scuba divers is complicated by the magnifying properties of water and the underwater environment. In this paper we describe the development and preliminary testing of an underwater stereo-video system which is designed to make accurate and precise measurements of the lengths of marine subjects. The results of 640 measurements of 16 plastic silhouettes of fish are presented. The initial results demonstrate the ability of the system to make accurate and repeatable measurements of length when the orientation of the subject to the stereo-video cameras is less than 75 degrees.