International research programs have endorsed knowledge co-production to enhance the utility and impact of global environmental change research. However, knowledge co-production frequently overlooks the complex interrelations between knowledge and power that permeate transdisciplinary sustainability research (TDSR). We analyse how power relations in transdisciplinary ocean governance projects form research agendas and design of six projects within the Belmont Collaborative Research Action on Ocean Sustainability, representing a broad set of experiences of transdisciplinary marine sustainability research practice spanning a wide set of sustainability issues and geopolitical contexts. We examine how distinctive forms of power shape the ways in which researchers envision socio-environmental change and transdisciplinary work within a spectrum of knowledge-action practices ranging from 'linear' to 'relational'. Our findings highlight the need for a deeper engagement with theories of change throughout the lifespans of transdisciplinary projects. Furthermore, the results point at constraints imposed by existing funding structures and epistemic assumptions on the ability of the projects to adopt relational transdisciplinary co-production research strategies, tailored to specific ocean contexts. We recommend adaptive funding structures which would allow researchers to exercise co-production agility and overcome the tension between the needs for embeddedness and transferability of insights. Finally, we show how the three forms of power interact in the linear and relational models of linking knowledge and action and suggest areas where researchers need to direct their attention when designing and implementing transdisciplinary projects aiming to promote sustainability action in close collaboration with societal actors.