This paper discusses the design of computer representation, based on a case study of computer animation projects in a university level design program. In the case study, a group of students reproduced the motions of living things on a computer, based on observations made in an aquarium. The following interpretations based on the “Situated Approach to Cognition” were derived from the examination of the case study. First, the computer representation of the motion of living things using methods such as “highlighting”, “plotting”, “semitransparency” is designed to visualize the motion of living things, not just copy that motion. The group of students “Localize” how to see the motion of living things by alternating between observation and representation, and using juxtaposed “Resources” such as additional computer animation, video movies of living things, references which describe the motion of the living things, and observations of “real” living things, and the developing representation and by referring to them mutually many times reflexivily. Second, the representation and the cognition of the motion of living things are here reconstructed and embedded in a situated environment of mutual social interaction among students and teachers, who share their ideas of problems in representing and cognizing the motion of living things through conversations and by viewing each others representations as their work progresses.