Marine litter is made up of flotsam and jetsam. Flotsam is the litter which is man-made and has made its way into the sea and jetsam has been deliberately put into the sea.

Marine litter orginates from a number of sources including beach users, sewage network, shipping industry, fishing industry, ocean currents carry litter from other countries and litter can been thrown or washed over board from vessels, urban runoff, oil rigs, agricultural waste, fly tipping, and aquaculture.

Marine litter is generally grouped into 8 categories. The biggest category is plastic, of which over 50% of marine litter is made up from. The other groups include glass, metal, cloth, paper and cardboard, polystyrene, rubber, wood and Sewage Related Debris or SRD, pottery/ceramics and munitions (phosphorous flares).