Through cross-disciplinary research a novel interactive tool has been developed, HullMASTER, which enables shipowners, operators, and authorities in the Baltic Sea region to make evidence-based decisions on strategies and policies related to ship hull maintenance. This novel tool is deployed as a standalone app (source code in MATLAB). Modelling is based on cost-effective approximate prediction methods (Granville method), as well as on empirical fouling data. Validation of HullMASTER predictions for hull-and-propeller performance shows ~80% agreement against nearly 40 vessel-years of performance data (fleet of 9 vessels). Further, three types of hull coating were compared in a demonstration case: a copper-based antifouling coating, a biocide-free foul-release coating, and an inert abrasion-resistant coating. In this demonstration, the foul-release coating is shown to be the most sustainable alternative for a 10,000-DWT cargo ship in terms of pressure on the environment and health. These societal savings are aligned with potential economic savings for the shipping operator.