Present understanding of the nature of water flows around swimming animals is almost entirely based on laboratory studies in confined tanks and flumes. Major technical limitations of such studies result in our knowledge being only an approximation to reality. With support of this grant the Principal Investigator, working with Prof. J.O. Dabiri and a postdoctoral associate, will carry out the first series of tests of a new technique and new apparatus for studying water flows around actively swimming animals under more natural conditions. The apparatus [Self-contained Underwater Visualization Apparatus (SCUVA)] is being developed in the laboratory of Prof. Dabiri at the California Institute of Technology. It is based on the use of the technique of digital particle imaging velocimetry (DPIV) together with digital video recording and scuba diving. Expected results will be a new tool to obtain quantitative, engineering quality, water-flow data from large, free-swimming, marine animals (porpoise and tuna). This study will provide substantial advances in our understanding of how animals swim, data that could lead to improvements in the design and operation of human engineered underwater vehicles and advanced training for a women postdoctoral associate in preparation for her entering a career in basic research and teaching.