The coastal environment is a major provider of goods and services, such as food, fossil fuels, construction materials, transport and recreation. It also hosts an invaluable biodiversity that forms complex ecosystems which are threatened by human activities such as agriculture, fisheries, aquaculture, shipping, urbanisation and tourism. Dedicated to the observation and monitoring of the European coastal waters is the Joint European Research Infrastructure of Coastal Observatories (JERICO-RI). The EU-funded JERICO-S3 project will provide a state-of-the-art, fit-for-purpose and visionary observational Research Infrastructure (RI), expertise and high-quality data on European coastal and shelf seas. The project will support world-class research, high-impact innovation and a window of European excellence worldwide. The project follows two previous EU funded projects: JERICO-FP7 (2011-2014) and JERICO-NEXT (2015-2019).