Hundreds of hardy swimmers across Britain braved jumping into freezing cold waters for a annual Christmas Day dip on December 25, 2017. (Photo by Dave Nelson/The Sun)

American media personality and socialite Kylie Jenner (R) and her pal Yris Palmer brave the cold in a hot jacuzzi in the first decade of December 2022. (Photo by kyliejenner/Instagram)

An Orangutan named “Pacquiao” and zoo owner Manny Tangco, wearing Santa costumes, embrace in front of Brown Philippine Deer while giving school children a tour ahead of the next week's Christmas celebration Thursday, December 18, 2014 in suburban Malabon city, north of Manila, Philippines. The yearly treat is aimed at encouraging residents to be sensitive to the feelings of animals especially when exploding firecrackers for the raucous celebration. (Photo by Bullit Marquez/AP Photo)

Nihon University professor and head of Nihon University Animal Medical Center Kazuya Edamura, 49, points to cat photos on a computer screen, which are used to train the AI of “CatsMe!”, an AI-driven smartphone application jointly developed by tech startup Carelogy and researchers at Nihon University that purports to tell when a cat is feeling pain, as he gives a lecture to students on diagnosing pain in cats, at the medical center in Fujisawa, south of Tokyo, Japan on June 11, 2024. (Photo by Issei Kato/Reuters)

Imagine living in the sea where it is permanently dark, cold, and food is hard to find. For many animals at depth, it may be weeks to months between meals. If you find something to eat, you have to hang on to it. This is why so many deep-sea fishes have lots of big teeth. This dragonfish, spotted off the coast of Australia, even has teeth on its tongue. They would be terrifying animals ... if they weren’t the size of a banana. (Photo by Julian Finn/Museum Victoria)

Trainer Lawney Hill poses for a photograph as she wears tights over her face to keep out the cold after taking her horses out on the all-weather gallops in Tetsworth, Britain, March 2, 2018. (Photo by Eddie Keogh/Reuters)

Women wearing "Shiroshozoku" or the traditional white robe pray as they bathe in ice-cold water at the Teppozu Inari shrine in Tokyo, Japan, January 10, 2016. About 100 participants took part in the Shinto ceremony to purify their souls and wish for good health in the new year. (Photo by Yuya Shino/Reuters)

Afghan vendors sort out oranges for sale at a wholesale market in the Bati kot district in Nangarhar province, Afghanistan, 04 December 2020. The orange fruit floods markets across Afghanistan due to bumper crop in the winter season. Oranges are rich in vitamin C, which may reduce severity of the common cold. (Photo by Ghulamullah Habibi/EPA/EFE)