Hi, each Line Body should be assigned a cross section and an orientation in DesignModeler/SpaceClaim Direct Modeler. In the Aqwa editor, when importing the geometry, each valid cross sections is automatically paired with a Beam Section object. Beam Sections are created under the Line Body Data object in the Outline tree. Apart from storing the geometric properties of the cross section, a Beam Section object also allows mass and hydrodynamic properties to be defined. In short, to have slender bodies (e.g. tubes) in Aqwa, you need first have their geometry in the SpaceClaim/DesignModeler as beams, and then Aqwa will automatically recognize them as Morsion elements. Details can be found in Aqwa User's Manual Section 5.5.2.
The disc doesn't need to be defined in the SpaceClaim. It can be added by right-clicking on a Part in the tree view in the Aqwa editor. Details about it can be found in Aqwa User's Manual Section 5.5.6.