Julian, left, is photographed by his mother with friend Gianluca, right, under water at a public pool in Gelsenkirchen, Germany, on a hot Friday, July 3, 2015. Germany faces a heat wave with temperatures up to 38 degrees Celsius (100 degrees Fahrenheit) at the weekend. (Photo by Martin Meissner/AP Photo)

Migrants react after boarding the Migrant Offshore Aid Station (MOAS) ship MV Phoenix some 20 miles (32 kilometres) off the coast of Libya, August 3, 2015. Some 118 migrants were rescued from a rubber dinghy off Libya on Monday morning. The Phoenix, manned by personnel from international non-governmental organisations Medecins san Frontiere (MSF) and MOAS, is the first privately funded vessel to operate in the Mediterranean. (Photo by Darrin Zammit Lupi/Reuters)

A 3-month-old ethnic Tujia baby girl is pictured next to her father as they wait for a traditional ethnic Tujia wedding feast during celebrations marking the Lunar New Year in Ziqiu town, Changyang county of China’s Hubei province, February 15, 2016. (Photo by Jason Lee/Reuters)

The Solar Impulse 2 airplane, flown by test pilot Markus Scherdel, flies off the coast of Oahu during a test flight from Kalaealoa Airfield in Kapolei, Hawaii, March 3, 2016. The solar-powered plane is ready to continue its revolutionary voyage around the world. After the craft was grounded in Hawaii last July due to overheated batteries, it was repaired and upgraded, and a recent initial test flight proved successful. (Photo by Eugene Tanner/Reuters)

A girl collects drinking water at Dala river outside Yangon, Myanmar March 3, 2016. Some 650 million people, or one in 10 of the world's population, have no access to safe water, putting them at risk of infectious diseases and premature death. Dirty water and poor sanitation can cause severe diarrhoeal diseases in children, killing 900 under-five a day across the world, according to United Nations estimates. (Photo by Soe Zeya Tun/Reuters)

Brazilian top model Gisele Bundchen poses before a fashion show by German designer Karl Lagerfeld as part of his latest inter-seasonal Cruise collection for fashion house Chanel at the Paseo del Prado street in Havana, Cuba, May 3, 2016. (Photo by Alexandre Meneghini/Reuters)

Baker Magadma, a member of Palestinian sports group Bar Palestine, performs on the street in Gaza City, on June 3, 2016. Street workout, which is still new in Gaza, is a growing sport across the world with annual competitions and events. (Photo by Mohammed Abed/AFP Photo)

Thousands of travellers heading to their hometowns to celebrate Eid al-Fitr, the Muslim holiday to mark the end of Ramadan, wait in a traffic jam to board a ferry at the entrance to Gilimanuk port on Bali, Indonesia July 3, 2016 in this photo taken by Antara Foto. (Photo by Nyoman Budhiana/Reuters/Antara Foto)