Stop peeing in the pool, already! Before you ask, yes, letting out a little twinkle while you're swimming in a pool really can affect you and the swimmers around you. (Gross, we know.) Here's what goes down: When urine binds with chlorine in pool water, it produces an irritant known as chloramine. This substance can cause eye redness in addition to respiratory problems. Urine isn't the only culprit, though — fecal matter, dirt, and sweat can also mix with chlorine, leading to symptoms from coughs to runny noses. Lovely, isn't it? Hopefully we didn't just ruin for swim session.