Lake Rebta, Senegal - Experts say the lake gives off its pink hue due to cyanobacteria, a harmless halophilic bacteria found in the water. It also has a high salt content, much like that of the Dead Sea, allowing people to float effortlessly in the pink water
Above, you see a genuine ad from Popular Science (1968), courtesy of newhousebooks. Below is the image that popped into my mind when I first saw it. Perhaps there IS an upside to sexist retro advertising after all?