A child looks at a polar bear swimming under a water in its enclosure on a hot summer day at Prague Zoo, Czech Republic, July 30, 2015. (Photo by David W. Cerny/Reuters)

In this July 25, 2015 photo, youth eat a cooked pig's head as they wait for the start of carnival in Santiago, Cuba. (Photo by Ramon Espinosa/AP Photo)

A herd of elephants cross a road that passes through the flooded Kaziranga National Park in the northeastern state of Assam, India, July 12, 2017. (Photo by Anuwar Hazarika/Reuters)

A man works on a tattoo during the 8th Expotattoo Colombia Fair in Medellin, Antioquia department, Colombia on July 14, 2017. The event – which is in its eighth year – attracted plenty of colourful characters. (Photo by Joaquin Sarmiento/AFP Photo)

Revellers dressed as zombies take part in an enactment of the running of the bulls a day before the start of the San Fermin festival in Pamplona, northern Spain, July 5, 2016. (Photo by Eloy Alonso/Reuters)

Participants play with water guns during the Sinchon Water Gun Festival in Seoul, South Korea, July 9, 2016. (Photo by Kim Hong-Ji/Reuters)

Revellers take part in the annual “Naval Battle” of Vallecas during the Virgen del Carmen Festival in Madrid, Spain July 17, 2016. (Photo by Javier Barbancho/Reuters)

Law enforcement officers clash with protesters, Wednesday, July 20, 2016, in Cleveland, during the third day of the Republican convention. (Photo by John Minchillo/AP Photo)