In the present work, the design and testing of two propulsion mechanisms which emulate fish swimming are presented. The motivation comes from the high effi ciency and maneuverality that
fi sh demonstrate over conventional rotary propellers. In order to know the fl uid fl ow pattern in detail, a 3D CFD model was developed. Details of the velocity and pressure fi elds were obtained,
as well as the hydrodynamic forces, cruising velocity, power and effi ciency. The results obtained using this CFD model were validated with the experimental prototypes, obtaining a reasonable agreement. Once validated, the CFD model was used to analyze several confi gurations of the propelling fi n, obtaining that thunniform swimming mode is the most effi cient
