This report sets out a vision for establishing National Marine Parks in the seas around Britain. Marine Parks could celebrate our biodiversity and heritage, improve public understanding and communicate the value of our coast and sea. They could improve stewardship by uniting communities to engage with and sustainably manage their local marine area. To explore the potential for Marine Parks in British waters, the Blue Marine Foundation explored maps and interviewed a range of stakeholders across Britain to discover areas where they could bring social, economic and conservation benefits. This is a summary of the research, offering insights for further discussion and debate. The report builds on the outcomes from a conference led by Blue Marine in 2018 and the learnings from a pioneering initiative in Plymouth Sound, where a National Marine Park was self-declared by the local community in 2019. This report proposes the start of a conversation about the purpose and benefits of National Marine Parks. It offers insights into some potential locations that might benefit, and some of the principles that might support their evolution from within communities to form a framework for National Marine Parks.