Many thousands of small oil spills occur each year. Oil spills occur due to negligence, the breakdown of equipment, natural disasters or deliberate dumping. These spills can be devastating to the environment and wildlife surrounding the epicenter of the spill. Thankfully, oil molecules are hydrophobic, meaning they mostly float on the surface of the water, making cleanup by boats at least theoretically possible.

When oil spills occur, the oil initially remains concentrated, but begins to rapidly spread in all directions as time passes, producing an oil slick. If oil spills are caught early, the cleanup technique of in-situ burning (burning in place) may be used. This is the most benign method of cleanup, but also one of the most rarely used methods. This is because the oil must have a minimum thickness of 3mm (0.12 inches) on the surface of the water in order to maintain a self-sustaining burn, and oil spills quickly spread out to thinner dimensions. Therefore, a boom, a type of corral which floats on the surface of the water, must be used to contain oil spills and artificially increase their thickness.

Special fireproof booms are used in conjunction with in-situ burning. When in-situ burning is infeasible due to the thickness of the spill, booms are used to contain the oil so that skimmers -- special boats with oil-absorbent plastics or vacuums -- can be used. Cleaning up large oil spills can be very expensive, tens or hundreds of millions of US dollars. Fines for spills are comparably severe. When an oil spill spreads out over a large area, it forms a sheen, a very thin rainbow-colored layer of oil on the surface of the water.

When cleanup with booms or skimmers is impractical, chemical dispersants must be used. Chemical dispersants are used to break down stray oil and lessen its impact on beaches and aquatic wildlife.

The largest oil spill in history was the Exxon Valdez oil spill in Prince William Sound in Alaska. Approximately 25% of the ship's 50 million gallons of oil was spilled, equivalent to approximately 125 Olympic-sized swimming pools. The ship collided with a reef due to a navigational error. Crew alcoholism and fatigue was blamed as the cause. 250,000 birds died from the incident. The event caused the United States Government to further increase the strictness of its fines and regulations meant to prevent against oil spills.