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)

Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

A seller dressed as Snegurochka (The Snow Maiden) shows Christmas toys at the Christmas decorations set in the Moscow GUM State Department store in Moscow, Russia in Moscow, Russia, Monday, December 16, 2019. (Photo by Pavel Golovkin/AP Photo)

Revellers enjoy air temperatures near freezing as they participate in the annual New Year's polar bear dip in the icy waters of Charlottetown harbour on Wednesday, January 1, 2020, in Charlottetown, Prince Edward Island. (Photo by Andrew Vaughan/The Canadian Press via AP Photo)

Wasibi, (r), yawns at backstage before the Algonquin Hotel’s Annual Cat Fashion Show in the Manhattan borough of New York City, New York, U.S., August 1, 2019. The theme of this year's show was “It's a Small World”. The cats represented countries including Ireland, Spain, the United Kingdom and the United States. (Photo by Jeenah Moon/Reuters)

Members of rival teams fight with oranges during an annual carnival battle in the northern Italian town of Ivrea, Italy on February 11, 2018. Established in 1808, the Carnival of Ivrea is one of the oldest and most particular festivals in the world. (Photo by Alessandro Bianchi/Reuters)

A man stands on a mountain summit as he looks over the Inntal valley in the western Austrian village of Gnadenwald, Austria on July 18, 2017. (Photo by Dominic Ebenbichler/Reuters)

Composite picture of lightning strikes over Colima, Mexico in just 5 minutes on July 14, 2020. These incredible photos show over 50 forks of lightning striking a city in just five minutes – in a storm being dubbed “The Night of a Thousand Forks”. The amazing, panoramic photos over the valley shows the whole sky light up as the forks of lightning strike at different points along the length of the city's 165 square miles. (Photo by South West News Service/Action Press)