Abstract: A device for linear propulsion (1) comprises a support structure (2) for carrying a payload, and one or more wave propulsion modules (3). The or each wave propulsion module (3) comprises a first individually-pivoted substantially planar blade (4) and a second individually-pivoted substantially planar blade (5). The first individually-pivoted substantially planar blade (4) is capable of producing a reactive force by self-attenuating by spring or dynamics of buoyancy means in response to an incoming fluid flow in the horizontal plane (6). The second individually-pivoted substantially planar blade (5) is capable of producing a reactive force by self-attenuating by spring or dynamics of buoyancy means in response to an incoming fluid flow in the vertical plane (7).