FAIR and open data sharing in support of healthy oceans, seas, coastal and inland waters Reuse of research data within and across disciplines and borders require openness, infrastructure capacity, better handling, careful management, machine actionability and seamless access to services all along the data life cycle. The Horizon Europe mission areas recognise upfront that providing access to data, knowledge and digital services through federated infrastructures is a key enabling condition for success. In addition, European Partnerships tackling complex societal challenges through multi-disciplinary approaches are facing important challenges in the European R&I systems, including poor data interoperability. In recent years, different scientific communities have started developing ‘thematic clouds’ or ‘data spaces’ within their domain of research and innovation. The EOSC provides the enabling framework to share, connect and upscale best practices and services by the communities to implement FAIR principles for (open, where possible) data sharing and management. The development of this framework is advancing rapidly as EOSC enters its second phase of implementation. Access to an initial EOSC federation of research infrastructures and their services is being consolidated and concepts such as FAIR data management and FAIR-by-design digital research outputs (data, publications, software, code, protocols, etc.) become more prominent.The overall objective of this topic is to accelerate research and innovation under this mission area through better access, management, interoperability, reuse and citation of digital information, to be achieved by using and integrating EOSC resources ranging from EOSC federated infrastructures, services and data to guidelines, best practices, tools and metrics for the management of FAIR and open data, and to extend these resources to the relevant marine and maritime domains that are less familiar with EOSC. This should be achieved through cross-domain, strategic use cases of direct relevance to the Digital Twin of the Ocean[[https://ec.europa.eu/info/funding-tenders/opportunities/portal/screen/opportunities/topic-details/lc-gd-9-3-2020]], the mission areas and the European Partnerships supporting this mission area on healthy oceans, seas, coastal and inland waters.The use cases should demonstrate the value of sharing FAIR and open research data, help to establish data sharing and management practices within the involved communities and across the Member States and Associated Countries, leveraging European research infrastructures and e-Infrastructures. The use cases should provide feedback to the EOSC Partnership on the desired future evolution of EOSC. Special attention shall be put on aspects of data harmonisation, data quality assurance, integration of data collection, data privacy and security, big-data analysis and machine learning methods, data and model validation, as well as on the socio-economic dimension of the use. Proposals should also foster the creation of user environments that researchers in this field can then use in order to seamlessly interact with digital information in the framework of the EOSC ecosystem.Proposals should provide for activities to collaborate with relevant European Partnerships. Synergies with Horizon Europe Cluster 6 activities and other relevant initiatives, including actions stemming from Cohesion policy programmes, are welcome. Research and innovation should build on results of Horizon 2020 (e.g. the Blue Cloud project, the Odyssea project) and support the development of the Digital Twin of the Ocean. Proposers should consider already established ESFRI research infrastructures and efforts by relevant ESFRI cluster projects.To ensure complementarity of outcomes, proposals are expected to cooperate and align with activities of the EOSC Partnership and to coordinate with relevant initiatives and projects contributing to the development of EOSC. In particular, in areas such as data interoperability, metadata and vocabularies, the use of persistent identifiers or AAI, proposals should coordinate and establish a feedback mechanism with the awarded proposal/s from the topic HORIZON-INFRA-2021-EOSC-01-05 in order to ensure alignment with EOSC policies and to identify common useful tools and resources as well as relevant data repositories that comply with EOSC guidelines. In this topic the integration of the gender dimension (sex and gender analysis) in research and innovation content is not a mandatory requirement.