However, some heavier oils are denser than freshwater and may sink to the bottom. Oil that sinks to the bottom of a water column is very difficult to clean up. Less dense oil also spreads more quickly, forming a sheen on top of the water that looks like a rainbow from above. Increased temperature also causes oil to spread quickly, while cold water causes the oil to solidify. There are many different ways to clean up after an oil spill.
Techniques vary depending on the size and location of the spill.
Sometimes, it is better to let the environment deal with the spill itself, and clean up efforts damage the ecosystem even more. If rare or endemic species are present, such as in the case of the Galapagos spill, then action should be taken quickly. If the spill occurs in deep water, or if the spill is headed quickly towards a sensitive area, the oil can be dispersed. Dispersal requires a receiving environment that must be more than 20m in depth. Chemicals and biological agents are added to the water to break up the oil into its chemical components.