An environmental activist adjusts his mask while taking part in “The Dead Sea Swim Challenge”, swimming from the Jordanian to Israeli shore, to draw attention to the ecological threats facing the Dead Sea, in Kibbutz Ein Gedi, Israel November 15, 2016. Swimmers from around the world plunged into the salty waters of the Dead Sea on Tuesday to attempt a seven-hour swim across the fabled lake in a bid to draw attention to its environmental degradation. Wearing protective masks and snorkels, 25 swimmers paddled through the muddy water to attempt the 9-mile (15-kilometer) swim from Jordan to Israel. (Photo by Nir Elias/Reuters)

In this aerial image, debris of the Japanese Imperial Navy fighter A6M “Zero” is seen in the field on August 29, 2016 in Babeldaob Island, Palau. The war was opened up 75 years ago by Imperial Japan against the allied forces, including the United States, by the Pearl Harbour attack on December 7, 1941, claimed more than 2 million lives until Japan's surrender in 1945. (Photo by The Asahi Shimbun via Getty Images)

A Ukrainian serviceman fires a 2S7 Pion self-propelled gun during military exercises near the village of Divychky in Kiev region, Ukraine, October 21, 2016. (Photo by Valentyn Ogirenko/Reuters)

JAPAN: A businessman stands at a pond in the Kyu-Shiba-rikyu Garden on a warm and sunny day in Tokyo, Japan, March 18, 2016. (Photo by Thomas Peter/Reuters)

A woman holds newly designed Indonesia Rupiah banknotes after exchanging her old bills at a Bank Indonesia mobile bank in Jakarta, Indonesia December 19, 2016. (Photo by Fatima El-Kareem/Reuters)

From the “Paradise Revisited” story in the November 2013 issue of National Geographic magazine, this image is a beautiful vision of father and son fishermen as they move through the multicolored coral gardens of Kembe Bay, Papua New Guinea, in a traditional outrigger canoe. (Photo by David Doubilet/National Geographic Creative)

An Iraqi military vehicle passes displaced Iraqi boys returning to their homes in West Mosul's Oreibi neighbourhood after government forces retook control of the area from the Islamic State (IS) group during the ongoing offensive against the jihadists on May 21, 2017. (Photo by Ahmad Al-Rubaye/AFP Photo)

A woman reacts as she attends a funeral ceremony for Mykola Kuliba and Serhiy Baula, servicemen from the “Aydar” battalion, who were killed in the fighting in eastern Ukraine, at Independence Square in central Kiev, Ukraine, May 26, 2016. (Photo by Gleb Garanich/Reuters)