WP4 provides a practical demonstration of how JERICO-RI Pilot Supersites (PSS) are to be implemented in order to become a network of Supersites, by establishing or improving their communication and steering at multiple levels, and their links to other observatories, RIs and regional initiatives. This deliverable reports the main activities of different PSSs and their Actions, including the main scientific and institutional advances. Within their regions, PSSs have provided a framework for thematic and interdisciplinary collaboration, joint use of resources, and planning and executing common activities. PSSs covered well a range of Key Scientific Challenges and Specific Scientific Challenges, set in JERICO-S3 WP1 as strategic objectives of making observations. PSSs also studied the organisational challenges, when implementing PSSs and moving towards sustained Supersites. This deliverable summarises the major findings for each PSS, analyses PSS implementation from the perspectives of the most commonly addressed Specific Scientific Challenges, considers integration aspects, from different points of view and analyses how PSS implementation period has improved JERICO-RI’s contribution to innovation and technology developments. In doing a self-assessment of PSS implementation, we conclude that JERICO-RI Supersites could be a key driver in the systemic change in coastal observations, towards integrated, regionally coordinated, transnational, multiplatform and multivariate observations. This would require a strong commitment from participating nations for sustained funding for transnational observing systems that are ultimately cost-effective and with higher capacity, but not for all parts under national control. We conclude by providing an outlook for JERICO-RI Supersites, by providing the key lessons learned during PSS implementation, listing additional needs for further integration and providing a future vision. The main conclusion is that JERICO-RI Supersites could be key elements in providing consistent pan-European data and products for the most complex coastal research questions, and as tools to meet the most demanding international commitments, but it requires consensus among participating nations to fund such developments.