Children in a mudfight

Photo: Bill Pugliano/Getty Images

Hannah Knupp, 10, of Livonia, Mich. is covered with mud by her friends at the annual Mud Day celebration in Westland, Mich. The annual summer event invites hundreds of children ages 12 and under to play in a mudpit created with 200 tons of topsoil and 20,000 gallons of water.
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Child and grandfather play in a fountain

Photo: Alex Wong/Getty Images

Christopher Szerszer cools off at a public fountain with his 2-year-old granddaughter, Nel, on a hot July day in the Georgetown neighborhood of Washington, D.C.
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People hula hoop in front of the White House

Photo: Pete Souza/White House

KidTribe hula hoopers perform on the south lawn of the White House during the annual Easter Egg Roll.
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Sumo wrestlers hold up babies

Photo: Junko Kimura/Getty Images

Sumo wrestling students hold babies up during a Crying Sumo competition at the Sensoji Temple in Tokyo, Japan. The first baby to cry wins the competition, which is a 400-year-old spring tradition inspired by the belief that a good, long cry is good for the health of the babies.
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Man slides down a long waterslide

Photo: Phil Walter/Getty Images

A man takes flight upon reaching the end of a 650-meter-long waterslide dug into a hillside in Waimauku, Auckland, New Zealand. Touted as the world's longest waterslide, the summer attraction was built by New Zealanders Jimi Hunt and Dan Drupstee to raise funds for Live More Awesome, a charity that raises awareness of depression.
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Young boy plays with a soccer ball

Photo: Jamie McDonald/Getty Images

A child plays with a football in the Khayelitsha township near Cape Town, South Africa.
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Woman cannonballs into a pool

Photo: Joe Raedle/Getty Images

A young women cannonballs into a campus pool filled with other students at Lynn University in Boca Raton, Fla., prior to an October debate between President Barack Obama and 2012 Republican presidential candidate Mitt Romney.
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Men celebrate a muddy soccer victory

Photo: Ingo Wagner/AFP/Getty Images

Members of the Iserlohn Grasshopper team engage in a muddy celebration after winning a match during the Second German Open Swamp Football Championship in Rieste, Germany.
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Young boy plays in a fountain

Photo: Gareth Cattermole/Getty Images

A young child frolics in a water fountain near the Wangfujing shopping district just before the start of the 2008 Olympic Games in Beijing, China.
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Catie Leary ( @catieleary ) writes about science, travel, animals and the arts.

9 happy moments in the great outdoors
If sumo wrestlers holding babies and mud-covered kids don't make you smile, it might be time you took a deep breath.