Recent developments in the global fuel markets imposed the need of increased fuel economy and cost effectiveness of sea-going vessels. Optimization of the ship's total energy system, as a whole, is now a demand of the marine industry sector in order to address the significant increase of installation and operational costs. This study is focused on the synthesis, design and operation optimization of a marine energy system. A realistic example of a cruise liner energy system has been selected. Basic technology options have been identified and a generic energy system model has been constructed. Various configuration options.. types of technologies and existence of components have been incorporated in the generic system. In addition, time varying operational requirements for this cruise liner ship have been considered, resulting in a time dependent operation optimization problem. The complete optimization problem has been solved using a novel algorithm, inspired by evolutionary and social behavior metaphors. A parametric analysis with respect to the fuel price demonstrated changes in the optimum synthesis of the system. (C) 2007 Elsevier Ltd. All rights reserved.