Some of the most famous incidents of water pollution have been oil spills. One was the Exxon Valdez oil spill which occurred when an oil tanker hit a reef off the coast of Alska and over 11million gallons of oil spilled into the ocean. Another bad oil spill was the Deepwater Horizon oil spill when an explosion at an oil well caused over 200 million gallons to spill into the Gulf of Mexico.