Climate change forces coastal communities exposed to floods to involve residents more actively in risk prevention, notably through official communication including behavioral recommendations. In order to improve prevention impact, this study aims to understand how inhabitants deal with this official information and integrate it into their relation to flood risk. This qualitative study is based on the theoretical postulate that the social dynamics nested in the relations between risk managers and inhabitants contributing to explain inhabitants' relationship to flood risk. These social dynamics are analysed through the type of trust granted by inhabitants to risk managers and the level of knowledge inhabitants state to have. 20 semi-structured interviews were conducted with inhabitants of a coastal city subject to flood hazards, recruited through snowballing method until saturation point. Results suggest that inhabitants who feel that they have little knowledge are prone to display social trust toward risk managers and a positive vision of communications provided on this risk, while those who are aware about floods, endorse a calculating trust based on the technical aspects of management, and eventually a form of distrust about communications delivered by public actors. These types of trust reflect a relation to flood risk embedded in the social space where individuals and groups take positions in social dynamics. In this sense and to be successful, preventive communication should consider not only the actual content of the message but also the social mechanisms that support its interpretation, in particular the trust between the messenger and the receiver.