A zookeeper feeds a hippopotamus with a watermelon in its enclosure in Belgrade's zoo, Serbia, July 20, 2015. Temperatures in Serbia have risen up to 40 degrees Celsius (104 degrees Fahrenheit), according to official meteorological data. (Photo by Marko Djurica/Reuters)

Atsushi Abe and Yumi Adachi from Japan perform in the synchronised swimming mixed duet technical routine preliminary at the Aquatics World Championships in Kazan, Russia July 25, 2015. (Photo by Michael Dalder/Reuters)

Members of Team Italy are seen underwater as they perform in the synchronised swimming team free routine preliminary at the Aquatics World Championships in Kazan, Russia July 28, 2015. (Photo by Michael Dalder/Reuters)

Protesters take part in “Artists Take Fight Against Police Murders” in New York's Times Square August 13, 2015. (Photo by Brendan McDermid/Reuters)

A worker holds harvested chillies at a chilli plantation in Pasir Datar Indah village near Sukabumi, Indonesia's West Java province, August 6, 2015. (Photo by Reuters/Beawiharta)

Topless activist Kaila J. walks through the rain following a “Free the Nipple” demonstration in Hampton Beach, New Hampshire August 23, 2015. (Photo by Brian Snyder/Reuters)

Samba dancers walk past a security staff member during the 34th annual Asakusa Samba Carnival in Tokyo August 29, 2015. About 5,000 people participated in the annual samba carnival on Saturday. (Photo by Toru Hanai/Reuters)

A Swiss police officer accompanies a migrant from Syria carrying her baby, upon her arrival at the railway station in the north-eastern Swiss town of Buchs September 1, 2015. (Photo by Arnd Wiegmann/Reuters)