A water transportation system of the kind in which a vessel is driven by a submerged moveable propulsion cable, particularly one which may assume greatly varying depth. The vessel is connected to the propulsion cable by flexible tension members, such as connecting cables, and there are winches aboard the vessel on which the connecting cables may be wound. The winches are controlled by electronic control equipment which, in addition to radio signals received from shore, is governed by tension and declivity sensors monitoring the connecting cables. Provisions of different kind are made available for changing the effective moment arm about the vessel centroid at which the members linking the vessel to the propulsion cable are connected to the hull longitudinally thereof.