A system for continuously laying a pipeline on a floor of a body of water is provided. The system includes at least one interchangeable reel for storing the pipeline to be laid; a pipelaying vessel to receive and support said reel, and to lay the pipeline from said reel into the body of water, an assembly and winding site to receive and support said reel, to assemble the pipeline to be laid, and to wind said pipeline on said reel and a crane to transfer the interchangeable reel from and to the pipelaying vessel.