Aquifers beneath sandy beaches act as land-ocean conduits for groundwater and are active biogeochemical reactors modifying chemical fluxes across the land-sea interface. Subterranean estuaries of high-energy beaches with large tidal and wave amplitudes could be particularly reactive due to the exchange of large seawater volumes and transport of marine derived constituents deep into the subsurface. In this study, we first present a new classification for coastal energy regimes as a function of mean tidal range and mean significant wave height and define the term “high-energy”. We establish a global distribution map of coastal energy regimes and classify porewater study sites in sandy beach aquifers related to their prevalent energy regime. Despite their extensive contribution to the global shoreline, the porewater biogeochemistry of high-energy environments is largely unknown. Through a of the few existing porewater studies at high-energy beaches we reveal patterns in morphology, hydrology, and biogeochemistry, describe promising research strategies, and highlight future research avenues in these challenging environments.