In this thesis the design, development and testing of a novel bio-inspired pectoral fin is presented and its possible applications are discussed. The fin was designed with a soft robotic approach, using SMA wires as tendon actuators and a body made of silicone, allowing to obtain a lightweight actuator, weighing approximately 47g, capable of producing forward thrust. The design was based on the paddle shaped fins of labriform swimmers, with possibility to independently move two rays placed in the extremities of the fin to perform different swimming patterns. The rays allowed a basic position control thanks to the presence of embedded flex-sensors, which was used to control the rays’ movement during the outstroke of the beat-cycle.