Marine optical imaging has become a major assessment tool in science, policy and public understanding of our seas and oceans. Methodology in this field is developing rapidly, including hardware, software and the ways of their application. The aim of the Marine Imaging Workshop (MIW) is to bring together academics, research scientists and engineers, as well as industrial partners to discuss these developments, along with applications, challenges and future directions. The first MIW was held in Southampton, UK in April 2014. The second MIW, held in Kiel, Germany, in 2017 involved more than 100 attendees, who shared the latest developments in marine imaging through a combination of traditional oral and poster presentations, interactive sessions and focused discussion sessions. This article summarises the topics addressed during the workshop, particularly the outcomes of these discussion sessions for future reference and to make the workshop results available to the open public.