A new report produced by the Interreg Med ACT4LITTER project reveals that marine litter is building up in what should be pristine coastal and marine protected areas. Wanting to dig deeper into the amounts, types and sources of marine litter deposited on the beaches of coastal and marine protected areas in the Mediterranean, the project set up a participatory-science campaign entitled ACT4LITTER Marine Litter Watch Month and assessed beach litter in a large number of locations in a consistent and harmonised way. The results and findings provide fit-for-purpose data for the effective management of marine litter in Mediterranean coastal and marine protected areas. Data of the marine litter campaign are referred to the winter edition, from mid Dec. 2017 till mid Jan.2018.