A plurality of sealed tubes, pipes or the like constituting the wall of a relatively large diameter pipe that is susceptible of being submerged and which has buoyant or semibuoyant walls. The tubes or pipes are arranged parallel to one another in a circular pattern with their axes parallel to the axis of the large diameter pipe and said tubes are sealed to one another along their length. A suitable clamping device is positioned upon said tubes or pipes to prevent them from collapsing over each other which acts as a positive stabilizer while maintaining said tubes or pipes in alignment in a circle.