National Geographic has created “Air, Land & Sea: the 50 greatest wildlife photographs” exhibition. Here: CT4 Crocodile cave on the Salamat river. Set up with Nathan Williamson last chip rain came while we were with the nomads. (Photo by Michael Nichols/National Geographic)

A reveller takes part in the Gay Pride Parade in San Salvador, on June 24, 2017. (Photo by Marvin Recinos/AFP Photo)

Reuters photographer Bobby Yip took a series of portraits of people taking part in the “Occupy Central” protests in Hong Kong, and asked them why they had joined the demonstrations. China rules Hong Kong under a “one country, two systems” formula that accords the territory limited democracy. Tens of thousands of mostly student protesters are demanding Beijing give them full democracy, with the freedom to nominate election candidates. The unrest is the worst in Hong Kong since China resumed its rule over the former British colony in 1997. (Photo by Carlos Barria/Reuters)

“After an afternoon of hiking and exploring the caves of Rhossili Bay, West Glamorgan, we caught the sun breaking through the clouds”. (Photo by Megan Warren-Davis/The Guardian)

A girl looks with comic disgust at a guy who falls asleep with a bottle of beer at a party; her friend laughs. (Photo by Edward Corbett/Rex Features/Shutterstock)

A model presents a creation by Spanish designer Agatha Ruiz de la Prada during the Mercedes Benz Fashion Week Madrid, MBFWM, in Madrid, Spain, 16 September 2016. The MBFWM runs from 15 to 20 September 2016. (Photo by J.J. Guillen/EPA)

A couple covered with the US and the pride flags pay their tribute for the victims of a 12 June mass shooting in Orlando, Florida, USA, as they look at the Eiffel tower, illuminated in rainbow colours, in Paris, France, 13 June 2016. A total of 50 people including the suspect were killed and 53 were injured in a shooting attack at an LGBT club in Orlando, Florida, in the early hours of 12 June. The shooter was killed in an exchange of fire with the police after taking hostages at the club. (Photo by Yoan Valat/EPA)

In this November 28, 1966 file photo, one of the 10 beagles involved in the first test of the Veterans Administration Hospital in East Orange, N.J. smokes a cigarette through a machine linked to its windpipe by a plastic tube to test any link between smoking and emphysema. (Photo by AP Photo)