Marine debris from ships and other ocean-based sources contributes to the spoiling of beaches, fouling of surface waters and the seafloor, and harm to marine animals, among other effects. International conventions and domestic laws intended to control marine debris have not solved the problem, in part because the laws provided little incentive to change behavior. Tackling Marine Debris in the 21st Century identifies ways to reduce waste, improve waste disposal at ports, and strengthen the regulatory framework toward a goal of zero waste discharge into the marine environment.