The notion of blended finance has increasingly gained traction within development policy as a way to fill a series of “financing gaps” related to the Sustainable Development Goals. Recently, blended finance has received increased attention as a way to create biodiversity markets and attract private capital. Building on qualitative research on efforts to create markets for private investments in marine conservation, this paper analyses how an ensemble of non-governmental organisations, development finance institutions and philanthropists seek to fill the financing gap for marine conservation in the “Blue Economy” by using blended finance as a guiding principle. I argue that by offsetting the uncertainties related to investing in a new conservation finance space, blended finance is applied as a way to fix investors’ fictional expectations and gradually transform uncertainty in risk. In doing so, this paper contributes to the literature on for-profit biodiversity conservation by highlighting how capital's risk interpretations are constitutive of the effort to create new markets. While blended finance is applied to create new markets from below, I discuss two other possible futures that might emerge as blended finance is applied in this new frontier. On the one hand, it risks becoming a development rent that is captured by the financial sector. On the other hand, blended finance can become a technical solution that enables the maintenance of a primordial faith in market-based environmental governance.