There's a bright pink-colored lake on one of the islands off the West Coast of Australia. It's called Lake Hillier and scientists recently determined the color is caused by a combo of algae and other microbes.
Up until recently no one really understood why it is the way it is ... but in essence, Lake Hillier is actually a pink salt lake. It has a high level of salinity and the color is suspected to be due to saltwater reacting with sodium bicarbonate (baking soda) or certain microorganisms—particularly salt-loving algae (dunaliella salina) and pink bacteria (halobacteria).
The Big Question, Is It Safe to Swim In? The answer is yes - it's absolutely safe to be in the water at Lake Hillier. In fact, it's safer than many other water sources due to the fact that there are no large fish or predatory species that reside in it.