A hull, suitable for use as a tension leg platform (TLP) or as a semi-submersible vessel, comprises columns having a generally polygonal transverse cross section at least one axis of which is generally radially aligned with the central vertical axis of the hull. Buoyant, subsurface pontoons interconnect adjacent columns. The pontoons are generally rectangular in cross section and the outboard, generally vertical surface of each pontoon is connected to a side surface of an adjoining column at a location which is substantially inboard of the outermost face of the column. In certain embodiments of the invention, tendon porches (configured to receive the upper tendon connectors of a TLP) are mounted to the outboard surface of one or more pontoons.