PIER is a cutting-edge maritime routing technology leveraging offline reinforcement learning combined with physics-based modeling and multi-objective optimization. It features a three-stage architecture that accurately predicts vessel speed, generates Pareto-optimal routes balancing time, fuel, and risk, and executes safe, fuel-efficient navigation with a formal safety shield. Tested in real scenarios like the Gulf of Mexico, PIER achieves significant CO₂ reductions and rapid computation, offering a scalable, simulator-free solution for the shipping industry.