Fin Actuator has an active span of 0.32 m. This actuation is provided by a 6 bar pneumatic source, coupled to three proportional valves, adjusting the input pressures. The deflected actuator is modeled as a curve of constant radius. It also presents a novel control problem in that the entire structure undergoes elastic deformation with no joints to control or measure. It consists of eight equally spaced PBAs arranged in a series along a mounting rail. Three proportional valves are used per PBA, enabling individual control of 3-d movements. The PBAs bend to act in a similar manner to the fin rays and are interconnected by an elastic material, acting as the fish fin membrane. The membrane currently used has been fabricated from a single sheet of two-way stretch Lycra, folded in half with a pouch created for each fin ray. Each sensor is a thin-walled aluminum pillar with a total of 12 strain gauges attached to its outer cylinder surface. The whole device is firmly attached inside a test tank.