A vehicle propulsion system having a mount; a rotation shaft oriented substantially normal to a plane of travel of a vehicle; a fixture coupled to the rotation shaft, the fixture being rotatable about a rotation shaft axis of the rotation shaft; and an oar assembly coupled to the fixture; wherein the coupling is coupled to the fixture, wherein the rotation shaft axis is substantially normal to the rotational axis; wherein the coupling is coupled to the fixture to permit rotation of the oar assembly about the rotation axis when the lock is locked.