Participants of the 77th edition of the annual Christmas swimming 'Coupe de Noel' jump into the waters of Lake Geneva, in Geneva, Switzerland, 20 December 2015. More than 1,540 men and women braved the water temperature of just 8 degrees Celsius as they swam a 120 meters distance at the traditional Christmas swimming in Geneva. (Photo by Salvatore Di Nolfi/EPA)

An athlete dressed as a clown jumps into the Mediterranean sea as he takes part in the Copa Nadal in the Spanish port of Barcelona in Barcelona, Spain, Sunday, December 25, 2016. The Copa Nadal (Christmas Cup) is a traditional swimming competition that takes place in Barcelona every December 25th, where participants swim 200 meters in the open sea in the port of Barcelona. (Photo by Manu Fernandez/AP Photo)

A swimmer disguised as Superman dives into the lake during the 78th “Coupe de Noel” (Christmas cup) swimming race in the Lake Geneva, on December 18, 2016 in Geneva. More than 1800 participants took part in the event, a 12-meter-long swimming off the Geneva's bank in the 7 degrees Celsius cold water. (Photo by Fabrice Coffrini/AFP Photo)

A three-month-old Sumatran tiger cub named “Bandar” shows his displeasure after being dunked in the tiger exhibit moat for a swim reliability test at the National Zoo in Washington, on November 6, 2013. All cubs born at the zoo must take a swim test before being allowed to roam in the exhibit. Bandar passed his test. (Photo by Manuel Balce Ceneta/Associated Press)

A woman wearing a swim suit skis during the Naked Pig Skiing Carnival at the Yabuli Ski Resort on March 24, 2018 in Harbin of Heilongjiang Province, northeast China. (Photo by Tao Zhang/Getty Images)

Atsushi Abe and Yumi Adachi from Japan perform in the synchronised swimming mixed duet technical routine preliminary at the Aquatics World Championships in Kazan, Russia July 25, 2015. (Photo by Michael Dalder/Reuters)

Members of Team Italy are seen underwater as they perform in the synchronised swimming team free routine preliminary at the Aquatics World Championships in Kazan, Russia July 28, 2015. (Photo by Michael Dalder/Reuters)

“Meet the woman dispelling the myths about one of the worlds most feared ocean predators by swimming without protection with great white sharks. Petite beauty Ocean Ramsey travels the globe swimming with many species of sharks hoping to prove they are nothing like their Jaws film reputation”. – Caters News. Photo: Ocean Ramsey freediving with a shark. (Photo by Juan Oliphant/Caters News)