Background The Greek seas host 14 threatened and critically endangered marine mammal species included in Annex IV of the Habitats Directive. The most notable nine are: Mediterranean monk seal (Monachus monachus), striped dolphin (Stenella coeruleoalba), common bottlenose dolphin (Tursiops truncatus), short-beaked common dolphin (Delphinus delphis), Cuvier's beaked whale (Ziphius cavirostris), sperm whale (Physeter macrocephalus), Risso's dolphin (Grampus griseus), harbour porpoise (Phocoena phocoena) and fin whale (Balaenoptera physalus). The long-term viability of these species is in imminent danger as a result of numerous human-related threats, including intentional killings; direct takes; accidental fisheries bycatch; prey depletion; collisions with vessels; disturbance; acoustic pollution (noise); ingestion of solid debris; contamination by xenobiotic compounds; oil pollution; habitat loss because of coastal development; and ecosystem and climate change. Objectives The Thalassa project’s objective was to mitigate the imminent danger, caused by human-related threats, to the long-term viability of all rare, endangered and important marine mammals inhabiting Greek waters. In order to achieve this, the project aimed to raise the awareness of selected target audiences about marine mammals in Greece, the importance of these species for marine ecosystems, the imminent threats they face, and the conservation actions necessary to ensure their long-term viability. A second aim was to establish a more active and environmentally-friendly attitude and behaviour in the target audiences and key stakeholders to directly promote and support the conservation of the Greek marine environment and marine mammals. Results The LIFE Thalassa project involved collaboration between MOm and associated beneficiary the World Wide Fund for Nature (WWF) Greece, and the participation of two research institutes: the Pelago Cetacean Research Institute and the Tethys Research Institute. It ran from September 2010 to December 2013. During this time, the project succeeded in raising the level of awareness of its target audiences, and helped to change attitudes and behaviour towards the marine environment and the 14 marine mammal species living in Greek seas. In the context of the communication strategy developed by the project, the Thalassa campaign produced a diverse range of high-quality awareness-raising, educational and capacity-building tools. Before and after public opinion surveys were conducted to record changes in the level of awareness, while quantitative evaluation methods were implemented to assess the communication tools' outreach and impact. The results of the survey conducted in 2013 showed a clear improvement in the general public's knowledge of the existence and need for protection of marine mammals in Greek seas, compared to the survey conducted at the start of the project. Public awareness of the existence of nine marine mammals rose from 82% in 2010 to 84% in 2013, but awareness increased from 80% to 91% in the key segment of the target audience aged 24-35 years. Awareness rose from around 13% to 35% regarding the fact that Risso’s dolphin and bottlenose dolphin inhabit Greek seas, after these species were featured in the project's TV and radio spots. The surveys also showed the public's improved knowledge of the threats faced by marine mammals. For example, awareness of collisions with boats rose from 47% to 56%, and of digesting solid debris from 83% to 91%. Both of these threats were featured in the project's printed media campaigns. In terms of measuring the willingness of people surveyed to participate in the conservation of marine mammals, the survey showed that there was an increase from 71% to 80% in those who were willing to stop consuming fish that are smaller than the legal size, while those who would avoid throwing garbage into the sea and on the shoreline increased from 70% to 77%. Campaigning tools developed to increase public awareness of marine mammals and their conservation included leaflets, print advertisements, two TV spots and two radio spots, a documentary and nine information videos (one on encounter instructions and eight on marine mammal species), posters and banners, a project website, eight issues of an e-newsletter, T-shirts, and two open events for the public. An internet awareness campaign was implemented targeting the 18-35 year old age group. This campaign involved the development of internet media platforms, including a Facebook page, Blog, YouTube and Vimeo channels, and Flickr and Twitter accounts. In addition, 16 websites and portals hosted the Thalassa e-banner. The Thalassa project’s environmental education campaign targeted children in kindergarten and primary schools, teenagers and educators. This campaign involved the development of the educational Thalassa Kit and the ThalassaPedia website. The Thalassa Kit was disseminated to 58 Environmental Education Offices and 35 schools, while 28 presentations of the Thalassa Kit were made in schools throughout Greece. Four seminars were organiser for educators regarding the Thalassa educational tools and activities. Key stakeholder advocacy and capacity-building campaigning targeted local and public authorities and decision makers, including members of the Greek Parliament and Greek Members of the European Parliament, as well as cadets of the Mercantile Marine and Navy Academies. The tools developed included the Greek Marine Mammal Conservation Handbook, the MPs and MEPs factsheets, and the electronic Capacity Building Kit. In total, 34 seminars were conducted in 22 cities throughout Greece and in Brussels reaching more than 1 000 attendees. The After-LIFE communication plan showed the commitment of both NGO beneficiaries to maintain and continue the implementation and dissemination of all the project's outputs. The communication tools developed by the project (e.g. website, social media accounts) have been maintained, for instance, while presentations prepared for the training seminars given to cadets were handed over to the professors of these academies to teach new groups of students. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).