The Blue Economy is an ocean based economic growth model gaining traction around the world. The way in which the Blue Economy is conceived and understood differs significantly across different sets of actors. A particular area of contestation exists around which ocean based industries or sectors can be considered to be 'Blue'. This highlights the possibility of the Blue Economy becoming a forum through which the legitimacy of different private uses of ocean resources is contested and debated. The question of legitimacy of Blue Economy activities and sectors is explored through a critical engagement with the notion of a 'social license to operate' (SLO). Whilst SLO is normally considered in the context of individual businesses or developments, in this article we explore the applicability of SLO at a cross-sectoral scale. In doing so we examine how the concept of SLO may inform debates over appropriate private use of public ocean resources, and how this might influence the legitimacy of the broader concept of a Blue Economy. A case study involving a range of private sectors actors engaged in diverse ocean industries was conducted, drawing on interviews, a cross-sectoral survey and an interactive workshop with the ocean business community. The case study explores the role that SLO is currently playing in ocean industries. In particular we explore perceptions of who grants a SLO, what kind of concerns impact a SLO and how sectors work to obtain, or maintain, a SLO. By comparing the responses of individual sectors to these three critical questions, we identify that many of the SLO challenges currently being experienced by ocean industries relate to conflicting social and political values. This is creating a range of complex, sometimes irresolvable, SLO challenges for maritime industries, largely concentrated in sectors engaged in resource extraction, such as mining and oil and gas. In addition we find that attempts to address SLO challenges to date focus mostly on technical or technological adaptations. When comparing this to Blue Economy narratives we find that current engagement with SLO speaks primarily to interpretations of the Blue Economy which favour growth based narratives, and largely neglect competing discourses. This has considerable implications for the overall legitimacy of the Blue Economy, as the loss of SLO within one sector may undermine the credibility of the concept overall. This research highlights the importance of broader societal and political engagement in questions about appropriate use and management of private sector activities in the ocean.