Aquatic ecosystems are characterized by an extraordinary mix of human activities (e.g., tourism, fishing, industry) and levels of protection. Given the often existing conflict of interests between conservation and exploitation, the fate of aquatic ecosystems is often a hot political issue; and the attitudes and values of stakeholders in environmental issues become an essential part of the stewardship of conflicting environments. New policies about environmental resources should have citizens’ support and consider public attitudes from the beginning. Even if participatory science is not new, it is going to be more and more important in the coming years. MPA’s managers, scientists and policy makers are seeking the best way to collect data and to interact with the audience about biodiversity issues. At the same time, global awareness and new technology give a larger public the opportunity to be part of environmental stewardship. Beyond the question of data reliability, this knowledge café proposes to explore, starting from many lessons learned, the questions that so many practitioners have to face up when a participatory program is set up and deployed.