In this May 2016 photo released by The Ocean Agency/XL Catlin Seaview Survey, a boat sails near a coral reef that has been bleached white by heat stress in the Maldives. oral reefs, unique underwater ecosystems that sustain a quarter of the world's marine species and half a billion people, are dying on an unprecedented scale. Scientists are racing to prevent a complete wipeout within decades. (Photo by The Ocean Agency/XL Catlin Seaview Survey via AP Photo)

An Israeli soldier takes part in during a rehearsal for a ceremony to mark Israel's Memorial Day for fallen soldiers at the Mount of Olives cemetery in east Jerusalem, Tuesday, May 10, 2016. Israel will mark the annual Memorial Day in remembrance of soldiers who died in the nation's conflicts, beginning at dusk Tuesday until Wednesday evening. (Photo by Oded Balilty/AP Photo)

Female Naval Academy plebes perform push ups with a twelve foot log on top of them during the annual Sea Trials May 17, 2016 at the Naval Academy in Annapolis, Maryland. The Naval Academy freshman class endures 14 hours of rigorous physical and mental challenges during the annual Sea Trials training exercise as part of the culmination of their freshman year at the academy. (Photo by Win McNamee/Getty Images)

Iraqi pro-government forces fire an anti-tank cannon near al-Sejar village, north-east of Fallujah, on May 25, 2016, as they take part in a major assault to retake the city from the Islamic State (IS) group. Iraqi forces, consisting of special forces, soldiers, police, paramilitary-fighters and pro-government tribesmen, launched a major assault to retake Fallujah, the scene of deadly battles during the US occupation and one of the toughest targets yet in Baghdad's war on the Islamic State group. (Photo by Ahmad Al-Rubaye/AFP Photo)

A 10-year-old boy living on the streets of New Delhi lies down on cascading water of a fountain in the gardens of the India Gate monument on May 20, 2016. The Indian Meteorological Department issued warnings of “severe heat wave” conditions across large parts of India's north and west, including the capital Delhi, where temperatures hit 47 degrees Celsius. (Photo by Roberto Schmidt/AFP Photo)

Colorado Gov. John Hickenlooper shows off his socks--one with Democratic presidential candidate Bernie Sanders and the other with Republican candidate Donald Trump – before entering his former brewpub for a book signing event to mark the release of his autobiography Thursday, May 26, 2016, in Denver. Hickenlooper, who is term-limited, is doing book talk rounds this week, reviving speculation that he is positioning himself to join Hillary Clinton's presidential campaign ticket. (Photo by David Zalubowski/AP Photo)

Chicken, fish and eggs lie next to coca paste worth $14,000 Colombian pesos at a local store in Guyabero Region, Guaviare, Colombia, May 24, 2016. As the government nears a historic peace deal with the rebels of the Revolutionary Armed Forces of Colombia (FARC), the nation's authorities are struggling to tame an increase in farming of coca, the raw material used to make cocaine. In the Guyabero Region, where many people work on coca plantations, locals barter coca paste to buy groceries at the local shop. (Photo by John Vizcaino/Reuters)

Tourist take pictures at Mai Khao Beach, as a plane approaches the Phuket International Airport in Phuket, Thailand March 17, 2016. With its palm-fringed beaches, Buddhist culture and racy nightlife, Thailand has been the poster child for Asian tourism for decades, attracting a range of visitors from backpackers and adventure-seekers, to families and culture vultures. But dark clouds could be forming even as a record of 32 million tourists are expected this year. (Photo by Athit Perawongmetha/Reuters)