The subterranean estuary (STE) plays an important role in controlling the fate of terrestrial and marine chemicals transported across the aquifer-ocean interface. A key distinguishing feature of STEs is their salinity structure, including the extent of seawater-freshwater mixing, which influences the biogeochemical conditions, and in turn the reactivity and fate of chemicals within the system. An increasing number of site-specific field studies have characterized the groundwater flow and salinity distribution within permeable nearshore STEs over the past 30 years. This study conducts a meta-analysis to collate available field data and explore the possibility of predicting the salinity distribution and mixing conditions in permeable nearshore STEs based on easy-to-measure or determine physical, hydrological, and oceanic parameters. Data from 39 individual field sites worldwide where the nearshore STE salinity structure has been measured were collated. Quantitative metrics were used to characterize salinity structure and mixing conditions at each site. The relationship between these metrics and the physical, hydrological and oceanic parameters of the field sites (e.g., tidal amplitude, wave height, beach slope) was evaluated. Overall, tidal amplitude was the only parameter significantly correlated with all salinity structure metrics. The correlations were stronger when physically meaningful combinations of the parameters were considered. Linear mixed-effects models suggest that the minimum salinity 1 m below the beach face seaward of mean shoreline may be predicted using tidal amplitude, significant wave height, and fresh groundwater discharge, suggesting that it may be possible to use this metric for classifying STEs as stratified, partially-mixed, or well-mixed systems.