A digital twin of a dynamic system or asset needs to combine monitoring of the states of the process/asset in question with mechanistic/physics based or data-driven models describing system dynamics. The main role of this chapter is to describe how the main aspects from Chaps. 1 to 5 may be synthesized into actionable Digital Twins for aquaculture. We first describe the general process of building a Digital Twin by combining the required components, and how this can be used to construct a digital representation of reality spanning the necessary dimensions to capture the full system dynamics. Following this, we explore how the necessary synthesis can be achieved using the knowledge and case studies presented in preceding chapters. This synthesis is examined in terms of capability levels that Digital Twins can achieve in aquaculture and how these compare with applications in other sectors, such as terrestrial livestock production. Finally, we present example applications of digital twins in aquaculture, founded in the topics presented in Chaps. 1 – 5 in this book. We conclude with reflections on future developments that will be critical to realize the full potential of digital twins in aquaculture.