PVDF actuators can be employed as a propulsion mechanism to miniaturise and simplify soft robotic fish for underwater exploration. Practical realization of soft robots such as robotic fish requires understanding a multitude of aspects, including fabrication and behaviour of the actuators, locomotion of the robot and application-specific electronics. Respectively, the literature review addresses these aspects. The main paper of this thesis examines the working principles of these actuators and develops an understanding of how they function in underwater environments. Various fish actuator designs, including samples with reinforced front stiffness, were fabricated using an enhanced airbrush printing platform. Comsol is used to model the soft robotic fish and actuator. The study examines the effects of PVDF annealing temperatures on maximum voltage and displacement. It also evaluates the interaction between electrode sheet resistance and water-resistant coatings. Fish performance and possible failures are explored. PDMS was found to have the least impact on actuator performance doubling the electrode resistance when applied to the top electrode layer. Samples annealed at 130 $\degree$C show higher maximum allowable voltage than 110 $\degree$C annealed samples, but maximum displacements are similar. Fishtail displacements up to 2.8 mm at 1640 V are measured in air, but no propulsion is observed when the fish is free-floating in water. Tail displacements of about 5 mm were observed at low frequencies in samples made with Novele substrate, which is five times larger than displacements at eigenfrequency. In contrast, the opposite effect was observed in fish samples using Kapton substrate. The observed motion at the eigenfrequency, when the fish was free-floating in water, is hypothesized to be too small, with whole-body vibrations instead of the expected tail-beating motion. The findings from this study provide insight into actuator capabilities and current fish design shortcomings. A deeper understanding of swimming dynamics may lead to future designs of soft robotic fish that can effectively propel themselves in water using PVDF actuators.