SEAO2-CDR is an ambitious multidisciplinary project that unites expert scientific, economic, legal, political, social and ethical researchers with industry leaders and regulators to establish and assess the evaluation pathways and methodologies required for sustainable and effective operationalisation of Ocean-based Carbon Dioxide Removal (OCDR). The implementation of appropriate CDR strategies is regarded as an essential component of most Net Zero emission pathways, yet the mechanisms and processes needed to facilitate their deployment remain largely unexplored. Notably OCDR approaches have generally received less attention than terrestrial CDR technologies despite offering equivalent, or greater, sequestration potential. SEAO2-CDR addresses critical gaps in our techno-economic understanding of archetypal OCDR approaches in order to define the operational spaces in which they are environmentally and economically viable, and will establish robust Monitoring, Reporting and Verification (MRV) strategies for different approaches using state-of-the-art Earth System Models (ESMs) and autonomous sensor technologies. Stakeholder-oriented governance frameworks will be developed that define the multi-dimensional interaction points through which responsible and effective governance of OCDR could be implemented and support the business development and investment needed to scale up OCDR. Finally, the parameterisation of ecological synergies and system-level trade-offs will enable OCDR to be incorporated into Integrated Assessment Models (IAMs) that identify which techniques are best positioned to support the transition to a climate-neutral and resilient society. Together these activities will enable SEAO2-CDR to advance the implementation potential of OCDR by supporting the characterisation and development of environmentally safe, socially acceptable, and economically viable approaches that can help realise global climate policies.