The fascinating reason why some Olympic swimmers wear two swim caps

NBC Sports Screenshot

Whether it's the type of bathing suit you wear, the way you jump off the diving board, or how much hair you have on your head, swimmers do a lot to make sure they get across the pool as fast as possible.

But you've likely never seen anyone wear two swim caps on their head at once.

SB Nation noticed that when gold medal-winning Hungarian swimmer Katinka Hosszu took off her swim cap, she revealed that she had another one on beneath it:

NBC Sports Screenshot

She's not alone — other competitors such as Team USA swimmers Michael Phelps and Katie Ledecky, as well as China's gold medalist in the men's 200 meter freestyle, Sun Yang, all wear two caps when they compete.

While it seems like any extra layers would slow a swimmer down, there's actually a really good explanation for it. During the 2012 London Summer Olympics, Pauline Vu explained the odd technique over at Yahoo.

The first reason is simple: It helps the swimmers easily keep their goggles from falling off their heads. Any swimmer can tell you that one of the biggest problems can be getting water-filled goggles. Wearing another tight swim cap on their head helps keep their goggles in place.

NBC Sports Screenshot

The second reason is a bit more interesting. Each cap is made out of different materials that compliment each other. The first cap is typically latex, which stays on the head better. However, it also "wrinkles." The second cap, which is made of silicone, doesn't wrinkle as much.

Thus, the less wrinkles, the less drag, and the faster a swimmer can go.

Vu notes though, that not everyone does this. But it further goes to show: Swimming isn't just a sport, it's an art form.

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