Groundwater-surface water interactions are an important process in coastal and estuarine environments that influence water budgets and bring bioactive solutes, such as nutrients, gases, and trace metals, yet are often overlooked. Submarine groundwater discharge (SGD), or the exchange of water between coastal sediments and surface waters, is a critical component of the global hydrologic and biogeochemical cycles that link terrestrial waters to marine environments. Fresh SGD, which may account for up to 10% of total freshwater inflows to the ocean globally, is a source of new nutrients to a system, whereas saline SGD is considered a source of recycled nutrients from sediments. Like surface water estuaries, within the coastal aquifer terrestrial and marine waters meet in a subterranean estuary where groundwater from land drainage is measurably diluted by seawater recirculating through the aquifer and altered to become biogeochemically distinct. SGD has been quantified in three Texas estuaries with Nueces Estuary consistently having the highest fresh SGD rates and Mission-Aransas and Upper Laguna Madre Estuaries being dominated by saline SGD. SGD-derived nutrient fluxes have been shown to be substantial in Texas estuaries but the influence of these nutrients on coastal ecosystem functions and services still requires further investigation.