Rivers are known for being wet. So how did a river in Ohio suddenly catch fire, not once, but several times last century? In part three of our water series, we'll explore the shocking tale of the Cuyahoga River. We'll look at how pollution led to this environmental tragedy and what's been done to address the problem. Plus, our Moment of Um explains why we say "ow!" when we're hurt.

See omnystudio.com/listener for privacy information.