This report summarises the key outcomes and lessons learned from Task 6.4 of the PREP4BLUE project, which aimed to build capacity and support stakeholder engagement under the EU Mission Ocean & Waters. The PREP4BLUE Stakeholder Engagement Helpdesk (HD) was developed as an online and expertdriven support structure offering guidance, tools, and personalised advice to Mission-funded projects. Its main purpose was to foster inclusive and effective stakeholder engagement by helping users identify and apply suitable resources and methodologies. In parallel, it promoted collaboration among the helpdesk teams of the four Mission Lighthouses, the Marine Implementation Platform (MIP), and the PREP4BLUE consortium. The helpdesk structure included a user-friendly online interface with curated resources on stakeholder engagement, citizen participation, Ocean Literacy, and knowledge transfer. Key materials included: • A Toolbox for Citizen Engagement • The Mission Ocean & Waters Social Media Toolkit and Digital Academy • The WaveLinks database of engagement-related initiatives • A shared Glossary to harmonise terminology • Recordings from both Citizen and Stakeholder Engagement Webinar Series • A Question and Answers section • A list of supporting experts • A form to facilitate interactions PREP4BLUE distinguished between citizens and other stakeholder groups, recognising that different engagement strategies and resources are required for individuals acting in a personal capacity versus those representing organised interests. The resources provided were tailored accordingly. Please note that this deliverable is still under review by the funding authority and may be subject to change.