Tourists play at a beach covered by a thick layer of green algae on July 3, 2013 in Qingdao, China. A large quantity of non-poisonous green seaweed, enteromorpha prolifera, hit the Qingdao coast in recent days. More than 20,000 tons of such seaweed has been removed from the city's beaches. (Photo by China Foto Press)

U.S. Army helicopters providing support for U.S. ground troops fly into a staging area fifty miles northeast of Saigon, Vietnam, August 28, 1966. Helicopter fuel is stored in the large rubber tanks, foreground. (Photo by Henri Huet/AP Photo)

Jason Ramsay and Amy Laverty, from Arbroth, Scotland, pose beside a large Christmas tree at Bondi Beach on December 25, 2016 in Sydney, Australia. Bondi Beach is a popular tourist destination on Christmas Day. (Photo by Don Arnold/Getty Images)

Photographers take photographs of the Large Air Tanker (LAT) C-130 Hercules, also known as “Thor”, as it drops a load of around 15,000 litres during a display by the Rural Fire Service ahead of the bushfire season at RAAF Base Richmond Sydney, Australia, September 1, 2017. (Photo by David Gray/Reuters)

Fishermen pull up a live 2.5 metre crocodile in their net in the Western Amazon region, Brazil on September 20, 2017. The fishermen were fishing for a large river fish called Arapaima but sometimes crocodiles become stuck in the nets as well. (Photo by Carl de Souza/AFP Photo)

Ukrainian teenagers hit each other with pillows during a large pillow fight in downtown Kiev, Ukraine, 24 April 2016. About hundred people took part in the event “Pillow battle 2016” in Kiev. (Photo by Roman Pilipey/EPA)

A woman covers her face as a fire burns in the middle of town during an anti-G20 protest on July 7, 2017 in Hamburg, Germany. Authorities are braced for large-scale and disruptive protests as Leaders of the G20 group of nations arrive in Hamburg for the July 7-8 G20 summit. (Photo by Leon Neal/Getty Images)

“Mr Big Dipper”, Nicholas Roemmelt (Denmark). A stargazer observes the constellation of the Big Dipper perfectly aligned with the window of the entrance to a large glacier cave in Engadin, Switzerland. This is a panorama of two pictures, and each is a stack of another two pictures: one for the stars and another one for the foreground, but with no composing or time blending. (Photo by Nicholas Roemmelt/National Maritime Museum/The Guardian)