In order to analyse problems with fluid flow, computational fluid dynamics is one of the most helpful tools available. This paper presents a numerical simulation of the effect of salinity on a marine propeller of an aircraft carrier in advance of the propeller open water (POW) test. A five-bladed fixed-pitch propeller is analysed using an unstructured mesh in the flow domain (PPTC - VP1304). Solving the RANSE equations describing the flow with a streamlined solver To begin, the accuracy of the numerical model was checked by comparing the results to previously published experimental data on the propeller. The verified model was then used to investigate how salinity impacted propeller performance in open water. The effect of fluctuating salinity was investigated by adjusting the properties of the flow fluid in a computational model. Lower advance ratios are where the effect of salinity, a decrease in efficiency of up to 4%, really shows up. However, it had little to no effect at higher advance ratios.