Over the years, bio inspired robotics has become of particular relevance, especially with the construction of systems capable of reproducing a fluid and noiseless motion, capable also of exploring and monitoring the marine environment. This work aims to model and realize an active biomimetic caudal fin, which guaranties the generation of a controllable movement through the utilization of SMA (Shape Memory Alloy) wires. The main objectives of this research are to design and develop a soft robotic structure capable of emulating the kinematic behavior of real caudal fins of fish. The study focuses mainly on deformation and actuation performance and to demonstrate the efficiency of using SMA as actuators for underwater use.