Quantitative assessment of animal swimming performance is essential to gaining an understanding the ability of aquatic species to compete in and withstand changes in their environment. A thorough understanding of swimming performance requires quantifying both the motion of the propulsors and the resulting fluid flow. For the myriad aquatic animals that use them, the ability to quantify simultaneously fluid flows produced by their various propulsors is constrained by the current methodological approaches that measure flow in only two dimensions. In this project, the investigators propose a novel 3D approach for studying swimming animals. They will focus on the two separate, but coordinated, propulsive systems of squid (jets and fins) as follows: (1) collect 3D data of the complete fluid flow (wake) generated by swimming squid (both fin and jet wakes simultaneously) and 3D kinematic data of the swimming motion; (2) apply new mathematical tools to quantitatively distinguish between hydrodynamic and kinematic patterns (i.e., gaits) based on their physical features; and (3) evaluate the propulsive performance (i.e., thrust and efficiency) associated with gaits identified in step 2. This quantitative approach will illuminate the selective pressures driving the structure, mechanics, and dynamics of the musculoskeletal system that powers and supports the propulsors. This research holds great promise for developing a universal framework for gait identification in any swimmer or flyer, especially those employing multiple propulsors, and thus may potentially transform current methods for studying locomotion. Beyond the field of biology, this quantitative, 3D approach could provide a valuable framework for engineers of bioinspired propulsion systems, who may be seeking improved propulsive performance in compact designs similar to what nature offers. Finally, the collaborative interdisciplinary nature of this project will allow undergraduate and graduate students with diverse backgrounds in physiology, biomechanics, and engineering to interact and acquire training in cutting edge technologies.