The boxed shaped vessel is a theoretical barge typically used as a simple example for the demonstration of basic hydrostatic principles. The vessel is perfectly rectilinear, though principal particulars vary, as well as form ratioes. The lack of hullform means simple geometry can be used for conditions of heel, trim, moments, & loads (whereas a ship-shape hull would require differentiation or Simpsons rules). Coefficients of form are also simularly simple (being 1.0).
Due to a large waterplane area for their size, barges exhibit large amounts of initial stability. Practically, however, a box or barge-shaped vessel often exhibit limited amounts of freeboard and thus reserve bouyancy. The consequence is a righting arm curve whose area is large, but limited to lower angles of heel. Depending on jurisdiction, some vessels may be able to gain a regulatory exemption, relaxing stability criteria at higher angles of heel in favour of more stringent requirements at lower angles of heel and operational restrictions.