Marine macrophytes represent a poorly constrained source of biogenic volatile organic compounds with potential implications for atmospheric chemistry and climate. This study reveals remarkable chemical diversity, detecting 166 compounds emitted by three common macrophyte species, with substantial variation among species and between geographic regions. The findings demonstrate that commonly studied compounds such as dimethyl sulfide represent only part of a much broader suite of marine emissions and highlight the need to account for environmental and population-level variability when estimating their contribution to global budgets. The study provides an important foundation for better integrating coastal macrophytes into our understanding of ocean-atmosphere biogeochemical exchange.