The occurrence of hull fouling is an unavoidable aspect of vessel navigation. The accumulation of fouling on a vessel’s surface leads to increased resistance to navigation, decreased propulsion efficiency, heightened energy consumption, and compromised vessel performance. To investigate the impact of varying levels of hull surface roughness and fouling attachment on navigation resistance, this study employs computational fluid (CFD) dynamics methods and conducts numerical simulations using FLUENT software. By referencing methods for estimating resistance under rough surface conditions and categorizing the degree of hull fouling, the severity of fouling attachment is determined based on the type of biological attachment and the density of fouling. Four distinct hull surface conditions are delineated, and corresponding models and conditions are established to analyze the effects of differing degrees of surface roughness caused by hull fouling on total vessel resistance and resistance characteristics. The findings indicate that poorer hull surface conditions result in greater increases in navigation resistance. Furthermore, under consistent surface conditions, the increase in navigation resistance correlates with higher speeds. Methods such as reducing speed and surface fouling removal are viable approaches for reducing navigation resistance across all surface conditions.