a deep water platform , suitable for use as a hydrocarbon exploration or production facility in very deep offshore waters , and a method of constructing the same are shown . the platform is positioned on top of a buoyant leg structure . during normal drilling operations the platform is anchored by a gravity base tethered with pre - tensioned cables to the buoyant leg structure . according to the invention , the gravity base is retractable to permit the platform to be moved from site to site within a drilling region . long distance relocation is also possible by retracting the gravity base , disassembling the platform , transporting the component parts , and reassembling the rig in a new location .