Viewed from above, Australia's Lake Hillier appears to be covered with Pepto Bismal. It's bright pink. The hue comes from the same algae that lives in San Francisco's salt ponds: the salt-loving Dunaliella bacterium. It contains pigment components that make it exceptionally effective at absorbing sunlight, resulting in the reddish-pink hue.
Scientists discovered a combination of algae and bacteria that contributed to Lake Hillier's pink tint. The lake's coloration can be attributed to the presence of microbes from a leather tanning facility in the early 1900s.
So, this example is half natural and half man-made; the lake's hue is very bright as a result of human activity.
