The paper regards with different basic approaches and methods for the parametric 3D representation of hull shapes in view of an automatic hydrodynamic optimization procedure. After a first selection of main dimensions of two fast frigate type ships, their geometric models have been developed inside the parametric surface modeling software Friendship-Framework, a leading CAE tool for the naval architects: different choices for the description of the hull shapes are presented and the potentiality of the models to represent also variations of the geometry itself, by means of changes of both global and local parameters, are shown.