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)

Vernon Yates, founder of Wildlife Rescue and Rehabilitation, lays his hands on Ty, a 400-pound tiger, as staff prepare to surgically extract a 4-pound hairball from the big cat, in Clearwater, Florida, on May 22, 2013. Ty is cared for by Wildlife Rescue and Rehabilitation in Seminole. The non-profit animal rescue group mainly serves by assisting Florida law enforcement with animals that have been seized. (Photo by James Judge/Courtesy BluePearl Veterinary Partners)

Two boys look out from the Mangueira slum towards the Maracana Stadium that is hosting the Rio's 2016 Summer Olympics opening ceremonies, in Rio de Janeiro, Brazil, Friday, August 5, 2016. (Photo by Leo Correa/AP Photo)

Pakistani youths cool off in a stream during hot weather on the outskirts of Islamabad on April 29, 2016. Pakistan's Meteorological Department has forecast hot and dry weather in most parts of the country with the highest temperatures recorded at 41 celsius in the southern Sindh province. (Photo by Aamir Qureshi/AFP Photo)

A man covered with dust sits on a street following a reported air strike by Syrian government forces in the rebel-held neighbourhood of Sukkari in the northern city of Aleppo on May 30, 2016. (Photo by Baraa Al-Halabi/AFP Photo)

Labourers break fast outside a shop in a market on the first day of the Muslim holy month of Ramadan in Karachi, Pakistan June 7, 2016. (Photo by Akhtar Soomro/Reuters)

Participants pose as they take part in a bodybuilding and fitness event named “China Fit”, in Beijing, China, June 15, 2016. (Photo by Reuters/Stringer)

A street vendor sells sliced fruits during a pro-government rally in Caracas, Venezuela, June 21, 2016. (Photo by Mariana Bazo/Reuters)