Marine oil spills are subject to natural processes, which alter oil's physical and chemical properties. These factors ? as well as the type of oil spilled, the magnitude of the spill, and the physical conditions of the spill site ? determine the appropriate response for spill cleanup. Response options include mechanical recovery, chemical treatment and in-situ burning. Every spill scenario is unique and constantly changing. Careful assessment by experienced personnel is required for effective response performance. Natural spreading of the oil spill is a major factor in determining the response option most likely to succeed. The number and availability of personnel and equipment is also a major consideration.