Lake Retba or Lac Rose lies north of the Cap Vert peninsula of Senegal, north east of Dakar. Depending on the time of day, the lake changes colour from a light purple to a deep scarlet pink. The unusual colouring of the water is caused by harmless halophilic bacteria that thrive in the lake’s high-salinity environment. The color is particularly visible during the dry season.

"The strawberry colour is produced by salt-loving organism Dunaliella salina. They produce a red pigment that absorbs and uses the energy of sunlight to create more energy, turning the water pink," said Michael Danson, an expert in bacteria from Britain's Bath University.

Covering an area of about 3 sq km, the lake is located about 35km north-east of Senegal’s capital Dakar. Since the 1970s, local residents have been mining Lake Retba for its salt, which they use mainly to preserve fish. Waist-deep in water, the men scrape the bottom of the lake to harvest this universally useful mineral which they collect in baskets in their wooden canoes. The salt is then taken back to shore where it is sectioned into small mounds. Dotted along the lake’s shore, these pristine white hills of salt create an arresting contrast against the pink of the lake. In order to protect their skin from the extreme salinity of the water, the workers rub their skin with shea butter, produced from shea nuts obtained from the Shea nut tree.

Lakes like Retba and the Dead Sea, which have high salt, were once thought to be incompatible with life. The salt content is very high, as much as 40%, which is almost one and a half times higher than in the Dead Sea - three hundred and eighty grams per liter. Lake Retba is well known for having been the end point of the famed Dakar Rally, which has since been relocated to South America.