The invention is a method for mooring a marine vessel (P) using three or more anchor lines (11a, 11b, . . . ) comprising—laying out each anchor line (11) with an anchor in a desired position relative to the platform, with a seabed anchor chain (10) extending towards the desired position of the platform (P), with the seabed chain (10) connected to a fiber rope's (20) arranged for being extended through the sea and connected to an anchor winch chain (30) and being tightended by an anchor winch (31) on the vessel (P), wherein the fiber rope (20) is prepared by being packed to a bundle or coil (21) arranged in a protective container (24) on the seafloor, and arranged for being released and pulled out of the container (24) at a predetermined pulling force, and arranged for being picked up and connected to the anchor winch chain (30).