The most common propulsive strategy of fishes and cetaceans is the Body-Caudal fin movement in which the animal undulates or oscillates its body, pushing backward the surrounding water. Most of the thrust is generated by the movement of the caudal fin, and every fish has a peculiar fin shape with a particular motion law, which determines different swimming performances. This thesis aims to understand the advantages and disadvantages of different fins both numerically, using CFD simulations, and experimentally, using a dedicated test bench. The experiments will be conducted at the Bioinspired Robotics Lab @ PoliMi Lecco.