Marine pipelaying method and system for installing an offshore pipeline (1) that includes one or more accessories (10). The method includes the steps of providing a vessel (2), launching the pipeline (1) in a firing line from the vessel (2) in the direction of the seabed, engaging the pipeline (1) with a clamping device (5b) that is connected to the vessel (2) and adapted to support the weight of the previously launched pipeline (1), and moving the accessory (10) into the firing line to a position above the clamping device (5b). Then the accessory (10) is connected to the pipeline (1) above the clamping (5b) device while the pipeline (1) is held by the clamping device (5b) Follow that the accessory (10) and the launched pipeline (1) connected thereto and releasably secured to a controlled load hoisting device (5) and the weight of the accessory (10) and the launched pipeline (1) connected thereto are transferred from the clamping device (5b) to the controlled load hoisting device (5) while the accessory (10) and the launched pipeline (1) connected thereto remain in the firing line. Finally the clamping device (5b) is disengaged from the pipeline (1) and moved away from firing line. Then the accessory (10) and the launched pipeline (1) connected thereto are lowered along the firing line by the controlled load hoisting device (5).