Offshore photovoltaic (PV) systems—especially those that use bifacial PV modules—offer tremendous promise for improving solar energy capture by capturing direct and reflected sunlight from the front and rear sides, respectively. Even so, the severe sea climate presents significant difficulties for solar systems as it expedites the degradation of PV modules and eventually lowers its operating efficiency. This paper presents a technique for predicting power degradation in offshore bifacial PV modules that considers salt stress and other climate factors. In this study, a cumulative damage model was tested to measure the combined impact of climatic stressors, including temperature fluctuations, relative humidity, ultraviolet radiation, and saltwater exposure, on offshore bifacial PV module’s performance, in contrast to current and previous approaches that examine climatic effects on onshore monofacial PV modules separately. A genetic algorithm is adopted to optimize model parameters, achieving high predictive accuracy. Real-world data validates the model, revealing a forecast accuracy of less than 1.1%.