We set out in this book project with the ambitious aim of achieving a better and more comprehensive understanding of the fragmented architecture of marine environmental governance in Europe, focussing on tensions between the Europeanization of regional seas and regionalization of EU policies. The question is – have we learnt anything about the identified key multi-level, multi-sector and multi-actor integration challenges (Kern and Gilek 2015 in this volume), or is the overall understanding of core problems still obscured by the complexity of the interactions? Furthermore, if in fact something has been learnt, can opportunities for improvements in practice be identified?