Plastic pollution is pervasive in world oceans and has gained large attention by the media, the public and the governments. The urgency of this issue was recognized by nearly 200 countries that signed in December 2017 in Nairobi the U.N. draft Resolution on Marine Litter and Microplastics. It has been estimated that 8 million tons (Mt) of plastic waste reaches the ocean each year, and with no action that volume is projected to double by 2030, and double again by 2050. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale 6. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean.