The Ocean presents a cacophony of sounds originating from natural as well as anthropogenic sources. Marine organisms heavily rely on sound to communicate and understand the world around them, and are therefore potentially impacted by anthropogenic sound. However, in developing our Blue Economy and in advancing our knowledge of marine environments and ecosystems, anthropogenic noise is sometimes unavoidable. Understanding the potential effects of anthropogenic noise is therefore integral to addressing this conflict, as it is needed to develop proportionate mitigation strategies and effective regulation. Next to providing an overview of our current knowledge about underwater noise, this publication highlights the priority areas for further research addressing the remaining knowledge gaps about the effects of anthropogenic noise. Furthermore, it points out the relevant actions needed to take in order to ensure ecosystem-based and precautionary legislation.