On 15 April 2014, BP announced that cleanup along the coast was substantially complete, while the United States Coast Guard work continued using physical barriers such as floating booms, the cleanup workers' objective was to keep the oil from spreading any further. They used skimmer boats to remove a majority of the oil and they used sorbents to absorb any remnant of oil like a sponge. Although that method did not remove the oil completely, chemicals called dispersants are used to hasten the oil's degradation to prevent the oil from doing further damage to the marine habitats below the surface water.