This paper provides the groundwork for the most efficient design of freshwater generating systems that take advantage of waste heat from the main engines. In the desalination process, freshwater generators, whether in the form of shell and tube-type or plate-type, are employed. Merchant vessels primarily utilize submerged shell and tube-type evaporators to generate fresh water. The foundation for comprehending separation processes, energetics, and economics lies in the quantitative interpretation of the second law of thermodynamics, with a specific focus on exergy and its dissipation. This research suggests employing exergy analysis to utilize waste heat as a valuable resource in a single-effect desalination process to meet freshwater needs, considering practical aspects. The study involves analyzing a freshwater generator of the Shell and tube type situated at the Tolani Maritime Institute in Pune, India. Thermal properties are calculated and visually represented through a flow diagram using a C++ program. The assessment of exergy unveils the extent and distribution of unattainable work within a freshwater generator employing a shell and tube design, particularly concentrated in its key components: the evaporator, condenser, and brine section. These findings are contrasted with those from a Plate Type Heat Exchanger (PTHE) freshwater generator. The rate of exergy destruction in Plate Type Heat Exchanger freshwater generators is 29.33%, whereas in shell and tube-type freshwater generators, it is higher at 44.88%.