Team GB synchronised swimmers Kate Shortman and Izzy Thorpe took on an underwater fashion shoot in June 2021 before they represent Britain in the artistic swimming competition at the Tokyo Olympics next month. (Photo by Bluebella/Cavendish Press)

This picture taken on September 11, 2023 shows Moon Jellyfish (with rings) and Sting Jellyfish (yellow-orange inside) among a smack of a several thousand swimming off Seglvik, in northern Norway. (Photo by Olivier Morin/AFP Photo)

A diver dressed in a Santa Claus costume swims at the Lotte World Aquarium in Seoul, South Korea, Monday, December 23, 2024. (Photo by Ahn Young-joon/AP Photo)

Neutral athletes Mayya Doroshko and Tatiana Gayday compete in the women's duet technical preliminary of artistic swimming at the World Aquatics Championships in Singapore, Friday, July 18, 2025. (Photo by Vincent Thian/AP Photo)

Members of the O’Neill and Gallagher families from Sydney, Australia take to the water at the 40 Foot for a Christmas Day Swim in Ireland on December 25, 2022. (Photo by Alan Betson/The Irish Times)

Lake Baikal is the world's oldest lake, at 25 million years (possibly older), and deepest, averaging 744.4 metres (2,442 ft).

Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the world, containing roughly 20% of the world's unfrozen surface fresh water.

A tourist splashes water on the frozen Songhua River on December 18, 2023 in Harbin, Heilongjiang Province of China. The water immediately freezes into ice in the frigid air. (Photo by VCG/VCG via Getty Images)

Paul Poirier of Canada and Marjorie Lajoie of Canada after training before the Figure Skating Ice Dance – Rhythm Dance at Capital Indoor Stadium in Beijing, China on February 12, 2022. (Photo by Aleksandra Szmigiel/Reuters)