 This paper proposes a new methodology for dividing the world's coastline into distinct segments based on their geographic and hydrological features. This approach combines existing methods of segmenting coastlines into river basins, estuaries, and continental shelves and then further refining them into 45 major zones and 149 subunits. These segments are then used to calculate various geographical and hydrological parameters, including surface area, volume, and freshwater residence times. Additionally, this methodology can be used to estimate the global estuarine carbon dioxide flux at the air-water interface, which is combined with regional data to provide a more accurate global picture. This article was authored by G. G. Larrell, H. H. Durr, R. Lauerwald, and others.