A protester uses molotov cocktails against riot police during May Day protests on May 1, 2010 in Athens, Greece. (Photo by Milos Bicanski /Getty Images)

Charlene Wittstock (L) and Prince Albert II of Monaco (R) attend the singles Final match between Rafael Nadal of Spain and Roger Federer of Switzerland on day nine of the Monte Carlo Masters Series tennis tournament. (Photo by Pascal Le Segretain/Getty Images). 2008

Wai Ching Jason Poon of Hong Kong competes in the Men's 1m Springboard preliminary round during Day One of the 14th FINA World Championships at the Oriental Sports Center on July 16, 2011 in Shanghai, China. (Photo by Feng Li/Getty Images)

Linda Cerruti of Italy competes in the Synchronized Swimming Solo Tech preliminary round during Day Two of the 14th FINA World Championships at the Oriental Sports Center on July 17, 2011 in Shanghai, China. (Photo by Ezra Shaw/Getty Images)

A novice Bhutanese monk sleeps after hours of prayer waiting for class to be over at the Dechen Phodrang monastery October 18, 2011 in Thimphu, Bhutan. The monks average about 10 hours of study a day waking up at 5:00am. (Photo by Paula Bronstein/Getty Images)

People purchase the book “Steve Jobs” by Walter Isaacson on launch day at Shanghai's City of Books on October 24, 2011 in Shanghai, China. The book was launched in 30 book cities at the same time across the country. (Photo by ChinaFotoPress/Getty Images)

A baby hippopotamus lies next to its mother on the first day it was presented to the public at the Zoo Berlin zoo on November 1, 2011 in Berlin, Germany. The baby hippo was born at the zoo on October 23. (Photo by Sean Gallup/Getty Images)

Boat crew members train on the waters of the Tonle Sap River on the morning of the first day of the Water Festival on November 13, 2016 in Phnom Penh, Cambodia. The yearly three-day Water Festival is one of the most important holidays in Cambodia and celebrates the end of the rainy season and the start of the rice harvesting. The Festival also coincides with the Tonle Sap river reversing course, which it does twice a year. Approximately 2 million people are expected to attend this year's festival, during which 259 boats and nearly 20,000 oarsmen will participate in the races. After a fatal stampede resulting in the death of some 353 people during the Water Festival in 2010, it has been cancelled four times over the past five years, with weather used as an official excuse. (Photo by Omar Havana/Getty Images)