AQUARIUS provides a highly comprehensive suite of integrated research infrastructures tailored to address significant challenges for the long-term sustainability of our unique oceans, seas, and freshwater ecosystems. For the first time, diverse research infrastructures are combined to facilitate the work of researchers and key stakeholders focused on challenges and opportunities for both marine and freshwater systems. The project comprises 57 services, including vessels, observation platforms, drones, satellites, sensors, and data infrastructure. It supports EU missions, the Sustainable Blue Economy Partnership, the European Green Deal, and international climate initiatives. AQUARIUS contributes to the European Digital Twin of the Ocean and the UN Decade for Ocean Sciences. Researchers will have access to funding through transparent Calls aligned with core objectives such as ecosystem protection, pollution prevention, and promoting a sustainable blue economy. Calls will focus on Lighthouse Regions like the Baltic and North Sea Basins, Black Sea, Atlantic/Arctic, and Mediterranean Sea.