While building a boat, a young mechanical engineer named C.M. Breder studied the movements of fish as inspiration. His experiments included removing one of their fins to evaluate how the change affected their mobility. After a few years of research, he constructed two models of metal boats based on how fish swim. The first boat was a flat, rectangular model which uses a metal detachable "tail" to steer itself. He used a phonograph motor as its engine so that each revolution nudged the tail. He called this model the "cow," saying that it demonstrated how a flexible tail and paddle-like fins could impel a fish forward. The second model, based on an eel, used a row of rigid wire rods covered by webbing to move around. A motor would push the rods back and forth, while the webbing would act like an underwater sail to give the boat extra momentum.
Read the full story in "A Sea Mystery Solved"