The majority of all marine debris is plastic. Calculations have shown that ten per cent of all plastic produced globally ends up in the sea. This plastic waste is subjected to both chemical and mechanical degradation. The sun's UV rays contribute to the degradation, as do waves, which cause plastic waste to grind against stones on the water's edge, against the sea floor or against other debris.

Garbage patches are large areas of the ocean where litter, fishing gear, and other debris - known as marine debris - collects. They are formed by rotating ocean currents called 'gyres', which act like a large whirlpool that pull objects in. The gyres pull debris into one location, often the gyre’s center, forming 'patches'. There are five gyres in the ocean. One in the Indian Ocean, two in the Atlantic Ocean, and two in the Pacific Ocean.

Garbage patches of varying sizes are located in each gyre. While some areas of the patch have more trash than others, much of the debris is made of microplastics.