Blood Falls is a massive waterfall located in Antarctica.
These falls were first discovered in 1911. Scientists believed that the red water was a result of algae.
It is now believed that two million years ago. a bunch of microbes were trapped under a thick layer of ice.
Over the years they have evolved into "primordial ooze" that is very rich in iron which causes the water to be red.
This must have been such a shocking discovery for those scientist in 1911.