Abstract: A system and method for mating risers or umbilicals extending vertically or near vertically from the ocean floor to a floating offshore system such as a TLP or semi-submersible platform. The risers or umbilicals are suspended vertically above the vessel's keel and are supported laterally near the platform's keel by keel guides or riser receptacles positioned along the submerged perimeter of the vessel's hull, or within the hull by production riser slots disposed in the bottom of the hull. The keel guides or production riser slots each receive a keel joint assembly which laterally supports a riser or umbilical passing therein while providing a bearing surface for free vertical movement of the riser.