The main purpose of this legislation, known as the Enhancing Science, Treatment, and Upkeep of America's Resilient and Important Estuarine Systems Act (or the ESTUARIES Act), is to improve the management and protection of estuarine systems in the United States. Specifically, it aims to reauthorize the National Estuary Program, which is designed to enhance the health of estuaries, areas where freshwater from rivers meets and mixes with saltwater from the ocean.