risers 12 extending downward to transport product to and from platform 10 platform 10 will be anchored by lines not shown not by riser 12 generally risers 12 are catenary risers extending downward from the platform and curving in a catenary curve to extend horizontally at the sea floor or some intermediate point beneath the surface however it is not necessary to this invention that riser 12 be of a catenary type rather it could be essentially vertical riser 12 is a tubular pressure containing member connected at one end to the destination or source of the product to flow therethrough such as a pipeline or christmas tree not shown referring to fig2 platform 10 has a catenary riser receptacle 14 positioned on its hull receptacle 14 is cylindrical having an upper conical end 16 and a lower conical end 18 which slope inwardly and toward receptacle 14 conical ends 16 18 help guide riser 12 and other lines into receptacle 14 the inner diameter of receptacle 14 is stepped into a plurality of diameters in a preferred embodiment there are four diameters with a first and largest diameter 20 near the lower end of receptacle 14 a second smaller diameter 22 is above the first diameter 20 and there is a first beveled transition 24 between the first and second diameters 20 22 a third diameter 26 is smaller than and positioned above second diameter 22.