Marine Regions is a LifeWatch-sponsored project whose purpose is to create a standard list of geographic names coupled with information and maps of their location. In August 2020, Marine Regions released a brand new data product: the High Seas. This data product delimits all parts of the ocean that are not under the control of any single nation (sometimes referred to as ‘international waters’). The dataset is a valuable addition to the already existing data products hosted by Marine Regions. As such, it will further benefit global ocean conservation initiatives and global fisheries management. For this new product, the Marine Regions team consciously made the decision to shift to FOSS tools. This has led to an improved and more reproducible workflow, leveraging the full potential of a suite of FOSS: QGIS, PostgreSQL/PostGIS, GeoServer and GeoNetwork. To make users more familiar with the OGC web services to consult and download the data, the web services tutorial page has been revamped. Additionally, the Marine Regions download page also offers GeoPackages as its first download option for all its products in order to encourage the adoption of open data formats. We discuss in detail how we use these FOSS tools throughout the various steps to create such a global GIS data product. One of those steps is for example the creation of a Pacific-centered version of the High Seas, for which various methods in R, QGIS and PostGIS were examined. Finally, we pinpoint remaining challenges that we would like to see resolved in the future. More info: www.marineregions.org. Contact: info@marineregions.org. Track – Use cases & applications Topic – FOSS4G implementations in strategic application domains: land management, crisis/disaster response, smart cities, population mapping, climate change, ocean and marine monitoring, etc. Level – 1 - Principiants. No required specific knowledge is needed.