Salt evaporation ponds, also called salterns, are shallow artificial ponds designed to extract salts from sea water. To make it's sea salt, many companies are using a method called "solar evaporation". Solar salt is produced by the action of sun and wind on seawater in large ponds. The seawater evaporates in successive ponds until the seawater is fully concentrated and the salt then crystallizes on the floor of the pond. Due to variable algal concentrations, vivid colors, from bright blue to deep red, are created in the evaporation ponds. The color indicates the salinity of the ponds.