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 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)

A squid in the Red Sea. Underwater photographer Andrey Nekrasov, 42, photographed bigfin reef squid in the pitch black Red Sea putting on an extraordinary light show when the sun goes down. (Photo by Andrey Nekrasov/Medavia/ABACAPress)

A new book published by the UK Natural History Museum showcases some of the most memorable underwater photographs taken over the last few decades in its annual wildlife photographer of the year competition. Here: Giant gathering by Tony Wu. “The first indication that something extraordinary was going on were the blows, huge numbers of them – the exhalations of huge numbers of whales. Entering the water, the photographer witnessed an extraordinary scene”. (Photo by Tony Wu/Unforgettable Underwater Photography/NHM)

These unique photos capture the moment a boy has his teeth picked clean by amazing underwater shrimp. These fascinating creatures spend their lives diving inside the mouths of fish to remove the parasites that lurk there. Russell Laman imitated the behaviour of the surrounding fish swarm to entice the cleaner shrimp into his mouth whilst snorkelling with his father Tim Laman in Bali, Indonesia. The 13-year-old queued with the waiting fish and then opened his mouth when the shrimps came near. (Photo by Tim Laman/Caters News)

Underwater photographer Sarah Lee uses a technique known as “duck diving” to capture these stunning photos of surfers in Hawaii. Surfers “duck dive” under the water to avoid incoming waves so they can get further out to sea. Photo: A surfer comes free from her surfboard. (Photo by Sarah Lee/Caters News)

“Alice in Waterland” is a beautiful series of photographs re-imagining the Lewis Carroll classic underwater. It’s a creation of photographer Elena Kalis, who lives on a small island in The Bahamas, surrounded, she says, “by pristine clear warm water. Underwater is where I spend a lot of time; snorkeling, diving, photographing. It is fascinating how the world changes down below: light, sound, gravity and proportions are different from what we are used to”. (Photo by Elena Kalis)

A girl watches as Saen Dao, an eight-year-old female asian elephant, and her mahout perform underwater during a show at the Khao Kheow Open Zoo in Chonburi south of Bangkok on June 1, 2017. (Photo by Roberto Schmidt/AFP Photo)