CommOCEAN2020, the 4^th international marine science communications conference. The event, arranged by the European Marine Board Communications Panel, is  hosted by the Institute of Oceanology Polish Academy of Sciences (IOPAN), and will see hundreds of marine science communicators gather together to discuss the issues facing the ocean, and to develop their skills and techniques with a core programme of inspiring and insightful addresses from leaders in marine science communication, presentations and workshops covering communications techniques and platforms, and examples of marine science research communication campaigns. The conference aims to build a strong community of marine science communication professionals from across the world, and to inspire inventive and effective communication of marine science within the science community, to the public, and to governments and policy makers. Registration is open for the conference via www.commocean.org and abstracts can be submitted for oral and poster presentations.