This paper describes innovation activities in the marine energy sector across ten European countries in 2011. Intense knowledge creation occurred in the UK and northern European countries, while European research networks encouraged public-private partnerships facilitating knowledge diffusion. An analysis based on a technological innovation system (TIS) has identified challenges for the system to evolve from one phase of development to another, i.e. from pre-development to take-off phase. In order for marine energy to pass successfully through the commercialisation 'valley of death', entrepreneurial experimentation and production is crucial. Entrepreneurial initiatives were developed mainly in the United Kingdom, Denmark, Norway and Ireland, whereas France, Germany and Sweden were active through venture capital initiatives. Additional system-builders, such as the authorities in charge of energy policies, could offer guidance for research, ensure legitimacy and effectively mobilise resources for system development. Although public support was efficient in stimulating private investment, national targets seemed less efficient in creating a long time horizon for private investors, due to consecutive, unexpected changes. In contrast, positive interactions between technology developers and policy-makers could empower market formation. Ultimately, the creation of a policy community, also involving local communities, could foster a positive environment for the development of innovation activities. (C) 2014 The Author. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).