Abstract: A method and apparatus operable to produce a continuous tension along at least a prescribed portion of pipeline as it is being assembled along the ocean surface and lowered to the ocean floor. The disclosed method involves the basic steps of: assembling an elongated pipeline above or adjacent to the ocean surface; placing at least a portion of the assembled pipeline under internal gas pressure to create a longitudinal tension along that portion of sufficient magnitude to prevent buckling as it is lowered to the ocean floor; and lowering the assembled pipeline onto the ocean floor. A portion of the lower section is filled with liquid to provide a gas tight seal and to prevent lateral movement of the lowered pipeline. The apparatus is comprised of a pair of inflatable bladders connected at opposite ends of a telescoping ram cylinder. This assembly is inserted into the assembled pipeline interior and is connected by a pressure tube and control lines to a barge where the pipeline is progressively assembled.