Liu et al., "Hydrodynamic Analysis of Webbed Foot for a Novel Biomimetic Robotic Duck"
My senior year I conducted research in a soft robotics lab, designing a foot for an amphibious duck-inspired robot. The main problem I focused on was a passive mechanism to generate thrust between the power and recovery strokes. I used an umbrella check valve style design, allowing water to pass through the foot during its recovery stroke, but not during its power stroke. I fabricated my own valves with a 3D printed mold.
minivalve.com
The proposed foot and valves!
This design was validated with an FEA simulation in ABAQUS and a CFD simulation in ANSYS Fluent. The simulation showed potential, but there was still substantial drag during the recovery stroke.