Sea salt is harvested by evaporating brine, i.e. ocean water, then scraping up the white bits. Obviously to industrialize this harvesting, you need to have your processing facility close to the shore. But for years food processing company Cargill, which has the highest revenue of any privately-held corporation in America, has been taking that a step further--in a visually-attractive way that can be seen by those flying over San Francisco Bay. It can also be seen on Google Earth:
What you're looking at are artificial ponds that Cargill pumps seawater into. As the water begins to evaporate and the salinity levels increase, certain microorganisms begin to thrive in the water. Initially algae begins to form, which causes the water to turn bright green.