Marine Environment is one of the most challenging conditions to which Reinforced concrete (RC) elements get exposed. Chemical attack by salts of Chloride and Sulphate poses corrosion threat to reinforcements thus decreasing the durability of RC elements. This incurs extremely high rehabilitation costs around the globe annually. Chloride ingress through diffusion is the major cause of rebar corrosion. Critical parameters influencing the chloride diffusion revolve around uncertainties. This brings grave importance for the reliability based approach for the prediction of service life of such structures in terms of probability of failure. This study focuses on the prediction of service life of an RC element taking epistemic uncertainties involved in the marine environment into consideration. COMSOL Multiphysics model has been used to simulate the chloride diffusion into the considered RC element domain with suitable boundary conditions. Key parameters like Surface Chloride Concentration, Diffusion Coefficient, Concrete Cover Depth, and Concrete Composition are considered for the simulations. Regression analysis is carried out and is coupled with the First Order Reliability Method to model the uncertainties of the critical parameters involved. This study will also play a vital role in quantifying the impact of various parameters, optimizing the design of marine structures, and to develop cost-effective management strategies.