Plastic, metal, rubber and paper are some of the materials that pollute the world's oceans, often in the form of soda cans, cigarette butts, plastic bags and bottles, and fishing gear.
Environmental and marine science specialists call it "marine debris," which, simply put, means anything in the ocean that wasn't put there by nature.
Recently, though, a new type of trash — microplastics — has become a focus for marine researchers, and they fear the impact of this type of debris may be especially dire.