Underwater tasks are diversified and articulated. The environment in which they must be accomplished is often unconstrained and unpredictable. Operating AUVs assuring safety of the robot and of its surrounding is therefore very difficult. On the other hand, many fishes are able to easily move in the same environments. A crucial factor for this capability is their body, which consists primarily of elastic and soft structures that enable both complex movement and adaptation to the environment.Among the most efficient swimmers we find rays, which show abilities like high speed turning and omnidirectional swimming. In this paper we propose an underwater soft robot based on the morphological features of rays. We mimic both their radially skeletal structure with independent actuators for each bone and the compliance of their fins. This flexibility of the structure provides an adaptive deformation that allows our robot to swim smoothly and safely.