Abstract: Power boat comprises hull having a keel line running from bow to stern which defines an axis of symmetry from which port and starboard hull portions of bottom surface extend to meet side walls. The stern of the boat is defined by a transom. A trim plate is mounted for pivoting about a transverse axis to alter the relative position of the bow in the water and control the wake-making or wake-shaping capability. A flat inclined surface slopes upwardly and sternwards from the transition point to form a water flow modifying part of the hull bottom surface. By rotating trim plate about hinge axis so that its trailing edge is lowered, the water flow encountering plate is deflected down and so the stern of hull can experience lift and the bow will “squat” or lower somewhat, with the keel line assuming a progressively lesser angle of attack to the surface of the water. This is accompanied by a change in shape of the wake (and some increase in drag).