A Ballet dancer prepares backstage during the final dress rehearsal for the famous Nutcracker ballet by Pyotr Tchaikovsky at the Joburg Ballet, Johannesburg, South Africa, 04 October 2018. The premiere of Nutcracker is scheduled for 05 October and the show will run for two weeks. (Photo by Kim Ludbrook/EPA/EFE)

This photo taken on August 7, 2016 shows mahjong enthusiasts playing mahjong under water in a swimming pool at a diving club in the Chinese city of Chongqing. Only participants with proper diving certification were allowed to take part in the underwater competition. (Photo by AFP Photo/Stringer)

This Wednesday, August 31, 2016 photo, provided by the Syrian anti-government activist group Aleppo Media Center (AMC), shows Syrian boys dive into a hole filled with water that was caused by a missile attack in the rebel-held neighborhood of Sheikh Saeed in Aleppo province, Syria. (Photo by Aleppo Media Center via AP Photo)

Sonam Kapoor, Jourdan Dunn and Lil' Kim attend the Ralph & Russo Haute Couture Fall/Winter 2016-2017 show as part of Paris Fashion Week on July 4, 2016 in Paris, France. (Photo by Samir Hussein/WireImage)

The Grand Canyon Skywalk is a transparent horseshoe-shaped cantilever bridge and tourist attraction in Arizona near the Colorado River on the edge of a side canyon in the Grand Canyon West area of the main canyon. USGS topographic maps show the elevation at the Skywalk's location as 4,770 ft (1,450 m) and the elevation of the Colorado River in the base of the canyon as 1,160 ft (350 m), and they show that the height of the precisely vertical drop directly under the skywalk is between 500 ft (150 m) and 800 ft (240 m).

This undated handout photograph released by Taipei City Zoo on July 17, 2013 shows recently born panda cub of giant panda Yuan Yuan in an incubator at Taipei Zoo in Taipei. (Photo by AFP Photo/Taipei City Zoo)

The British rock and roll group the Beatles talk to Ed Sullivan at CBS Studio 50 before their live television appearance on “The Ed Sullivan Show” in New York, February 10, 1964. From left to right are, Sullivan, John Lennon, Ringo Starr, holding a cigarette, and Paul McCartney. (Photo by AP Photo)

A newborn baby giraffe shows its tongue at the Planckendael zoo in Mechelen, 25 kilometers North of Brussels, Tuesday, February 18, 2014. The calf was born on Valentines day, February 14, and has a heart shaped spot on the hip. (Photo by Yves Logghe/AP Photo)