Men slide in the mud during the Boryeong Mud Festival at Daecheon Beach in Boryeong, South Korea, Saturday, July 22, 2017. The 20th annual mud festival features mud wrestling and mud sliding. (Photo by Ahn Young-joon/AP Photo)

Planes land in fog at Heathrow Airport, west London, as heavy fog covers a many parts of the south east, on April 1, 2014. (Photo by Steve Parsons/PA Wire)

Palestinian female Hamas security officers demonstrate their skills during a graduation ceremony in the northern Gaza Strip, Wednesday, April 2, 2014. 1200 officers graduated from advanced training courses that lasted one year in Gaza police academy of Hamas. (Photo by Adel Hana/AP Photo)

This Thursday, January 22, 2015 photo made with a long exposure shows the glow from a Noctiluca scintillans algal bloom along the seashore in Hong Kong. The luminescence, also called Sea Sparkle, is triggered by farm pollution that can be devastating to marine life and local fisheries, according to University of Georgia oceanographer Samantha Joye. Noctiluca itself does not produce neurotoxins like other similar organisms do. But its role as both prey and predator tends can eventually magnify the accumulation of toxins in the food chain, according to R. Eugene Turner at Louisiana State University. (Photo by Kin Cheung/AP Photo)

A woman walks against blowing snow in Evanston, Illinois, on February 8, 2014. (Photo by Nam Y. Huh/Associated Press)

Protesters shield themselves as police beat them with sticks during a violent demonstration near the India Gate against a gang rape and brutal beating of a 23-year-old student on a bus last week, in New Delhi, India, December 23, 2012. The attack last Sunday has sparked days of protests across the country. (Photo by Kevin Frayer/Associated Press)

Saudi youths demonstrate a stunt known as “sidewall skiing” (driving on two wheels) in the northern city of Tabuk, in Saudi Arabia December 3, 2014. (Photo by Mohamed Al Hwaity/Reuters)

A frightened maid, played by Phoebe Hodgson, knocks a bust off a tall pedestal while dusting, in a scene from the play “Queen High” at the Queen's Theatre. (Photo by Sasha/Getty Images). 1926