Ship hydrodynamics is a core discipline in marine engineering and has been for many decades. In addition to the sea keeping and manoeuvrability, the power demand for propulsion is subject of every ship’s design. Nevertheless, the possibilities for reducing the energy required to propel ships are far from exhausted and are becoming increasingly relevant. Experimental and numerical methods allow thorough optimization, while, in the context of the decarbonization of the transport sector and the associated rise in energy costs, the relevance of optimization objectives is shifting. The possibilities for holistic optimization are limited for the existing fleet. Nevertheless, considerable hydrodynamic savings are possible. This also includes what at first glance appears to be an extremely radical measure that is so far only considered for inland shipping: the so-called aft-ship replacement. This article presents the approach and potential based on a case study for a typical 50-year-old inland waterway vessel. The hull geometry of the existing vessel and corresponding power demands in realistic water depths served as the baseline for parametric form optimisation with an automated meshing and CFD workflow.