Abstract: A robotic device for navigating in at least a liquid medium, includes a legged propulsion system having a series of legs external of a body of the robotic device, each of the legs being independently driven and mounted to the body for pivotal movement about a respective transverse axis. The legs oscillating relative to the body about the respective transverse axis such that interaction between the legs and the liquid medium produces propulsive forces that displace the robotic device within the liquid medium. A control system is operatively connected to the legged propulsion system for autonomous control and operation of the robotic device based on information received from at least one sensor providing data about an environment of the device.