Abstract: A method of laying a flexible member below the bed of a body of water comprising forming a trench in the bed and laying in it a line having a greater strength and/or a lower cost than the flexible member; and then in a separate second operation laying the flexible member from a cable-laying ship in substantially the same trench by submerged apparatus caused to follow the path of the line. Usually the line will be buried before the second operation commences, and the submerged apparatus then takes the form of a submerged plough which re-forms a trench, on substantially the same route as the original trench. The technique allows the flexible member to be laid on a route known to be free of obstruction.