[This dataset is embargoed until December 15, 2026]. Sites were monitored for key water quality indicators, including: water quality parameters (temperature, pH, electrical conductivity, salinity, dissolved oxygen and turbidity), water samples collected for subsequent nutrient analysis (for dissolved inorganic nitrogen and phosphate), and where possible seagrass or algal samples were collected for isotopic composition. Water quality data was collected across a range of sites in Laamu atoll between 2022 and 2024 to develop a baseline understanding of water quality, to help characterise nutrient loading and identify potential sources of nutrient pollution. The sampling was conducted on varying spatial and temporal scales. This included a variety of island types (e.g., inhabited, uninhabited, agricultural, tourism islands, pristine patch reefs), and within individual islands. Sampling was conducted across a spectrum of uses-types of different sites (e.g., densely populated areas, versus heavy agricultural areas, vs rural areas etc) between different seasons (wet and dry seasons) on monthly, quarterly, bi-annual and annual time-windows. Repeat sampling was conducted on several sites several times a year and over 2 years to get a sense of change over time and within season.