In order to ensure relevance and societal impact of research and to meet the various requirements of different target groups, the Coastal Observing System for Northern and Arctic Seas (COSYNA) developed and pursued a broad range of activities for knowledge transfer and stakeholder interaction. Potential user groups of data and data products include (but are not limited to) science, administration, renewable energies, engineering, tourism, and nature conservation. COSYNA data and data products are publicly accessible and available free of charge via the Internet (data portal; www.cosyna.de). The stakeholder interaction is integrated into the COSYNA product life cycle outlined here and the steps undertaken are exemplified for the product Surface Current Fields in the German Bight. Initial surveys revealed COSYNA's potential relevance in the national and international context. After the technological and mathematical realization of high-quality parameter fields, external experts evaluated the scientific value, informational value, innovative leap, cost/benefit aspects, operability, etc., of the data products. In order to improve products and their usability and to pave the way for future co-operation, interviews and workshops with potential users from the offshore wind energy industry were conducted. The stakeholder interaction process was successful, revealing relevant insights into user demands and usability of (possible) products. Analysis of data download provided some evidence for impact beyond academia. Other criteria for the increasingly demanded evaluation of the impact of coastal research are discussed. By sharing first-hand experiences, this study contributes to the emerging knowledge on integration of science and end users.