We propose actions to guide collaboration between ‘natural’ and ‘social’ science disciplines in marine environmental issues. Despite enthusiasm for interdisciplinarity on environmental issues, institutional and disciplinary barriers remain for interdisciplinary working in practice. This paper explores what natural and social scientists need from each other for more effective impact assessment in the marine environment. We reflect on collaboration between natural- (especially marine biology) and social scientists (especially environmental sociology) researching the Tomakomai CCS Demonstration Project in Japan; including subsequent expansion of the research team and wider evaluation of project outcomes. We identify two areas of mutual support: community and stakeholder engagement on marine monitoring; and identification of points in regulatory/policy processes where qualitative findings may gain traction alongside quantitative results. We suggest interdisciplinary collaboration for marine environmental research could be helped by making time to learn from each other within projects; and by working together more closely in the field.