The SeaDataNet pan-European infrastructure has been developed by NODCs and major research institutes from 34 countries. Over 100 marine data centres are connected and provide discovery and access to data resources for all European researchers. Moreover, SeaDataNet is a key infrastructure driving several portals of the European Marine Observation and Data network (EMODnet), initiated by EU DG-MARE for Marine Knowledge, MSFD, and Blue Growth. SeaDataNet complements the Copernicus Marine Environmental Monitoring Service (CMEMS), coordinated by EU DG-GROW. However, more effective and convenient access is needed to better support European researchers. The standards, tools and services developed must be reviewed and upgraded to keep pace with demand, such as developments of new sensors, and international and IT standards. Also EMODnet and Copernicus pose extra challenges to boost performance and foster INSPIRE compliance. More data from more data providers must be made available, from European and international research projects and observing programmes. SeaDataCloud aims at considerably advancing SeaDataNet services and increasing their usage, adopting cloud and HPC technology for better performance. More users will be engaged and for longer sessions by including advanced services in a Virtual Research Environment. Researchers will be empowered with a collection of services and tools, tailored to their specific needs, supporting marine research and enabling generation of added-value products. Data concern the wide range of in situ observations and remote sensing data. To have access to the latest cloud technology and facilities, SeaDataNet will cooperate with EUDAT, a network of computing infrastructures that develop and operate a common framework for managing scientific data across Europe. SeaDataCloud will improve services to users and data providers, optimise connecting data centres and streams, and interoperate with other European and international networks.