Numerical modeling has proved itself to be an indispensable tool to support policy making with quantitative estimates. Be it of the effects of future changes or the effectiveness of proposed measures or strategies. This is no different for coastal hydrogeology, where numerical modelling has been in use for decades to predict future freshwater availability, support well design, and model the effects of climate change and sea level rise. However, due to the calculation times generally associated with coupled variable density groundwater flow and salt transport models, these models have been generally applied at the local to regional scale. In 2020, we developed a nationwide variable density groundwater flow and salt transport model for the Netherlands, the LHM fresh-salt. The model makes use of a parallelized version of SEAWAT, and was built using a reproducible scripted workflow. Model parameters are based on the existing Netherlands’ nationwide regular groundwater flow model LHM, with additional procedures put in place to resolve transport-specific problematic parameter combinations. The resulting model consists of over 31M active cells, calculation time originally was about 75 minutes per year on 24 CPUs. Five years on, the LHM fresh-salt model has undergone several version updates, has been used in studies ranging from national policy studies, investigating effects of sea level rise scenarios for the Netherlands and defining National Groundwater Reserves, to more regional scale studies investigating possible brackish groundwater extraction or optimizing regional water management. We experienced that the readily availability of the LHM fresh-salt model spurred its use, while both user trust and version updating benefited from its reproducible construction. Future developments include changing to the MODFLOW6 framework and further incorporating the LHM fresh-salt model in the wider LHM model framework.