This report draws together scientific understanding of deep-water sponge grounds alongside the threats they face and ways in which they can be conserved. Beginning with a summary of research approaches, sponge biology and biodiversity, the report also gives up-to-date case studies of particular deep-water sponge habitats from around the world. This report considers the international policy context in which deep-water sponge grounds can be conserved and concludes with a series of expert recommendations for conservation managers and international policy makers.