A young visitor interacts with a baby hippopotamus swimming in its enclosure at the Berlin Zoo on January 1, 2018. Tourists and locals flocked to the zoo in the German capital on the unseasonably warm first day of the year. (Photo by Odd Andersen/AFP Photo)

Villagers from the Medio Jurua nature reserve of Brazil's Amazon rainforest arrive with their catch of pirarucus, the largest freshwater fish in South America, after a night of fishing in Manaria Lake, Carauari municipality, September 3, 2012. Catching the pirarucu, a fish that is sought after for its meat and is considered by biologists to be a living fossil, is only allowed once a year by Brazil's environmental protection agency. (Photo by Bruno Kelly/Reuters)

A young woman cools herself in a fountain in Budapest, Hungary July 6, 2015. Over the weekend, a heat wave has reached Hungary with temperatures topping 38 degrees Celsius (100.4 degrees Fahrenheit). (Photo by Laszlo Balogh/Reuters)

American Yoga teacher Dashama poses on a Yoga-board during a preview of the 46th International Boat Fair in Duesseldorf January 16, 2015. The BOOT 2015 watersports fair, with more than 1,600 international exhibitors will run in Duesseldorf from January 17 to January 25. (Photo by Ina Fassbender/Reuters)

In this undated photo made available by journal Nature on January 15, 2014, a northern bald ibis (Geronticus eremita) flies in Tuscany, Italy. A new study released Wednesday, January 15, 2014 says the birds choreograph the flapping of their wings, getting a boost from an updraft of air in the wake of the flapping wings by flying behind the first bird and off to the side. When a flock of birds take advantage of these aerodynamics, they form a V. (Photo by Markus Unsöld/AP Photo)

A performer presents a creation from the Haute Coiffure Fall-Winter 2014/15 collection by French designer Charlie Le Mindu during the Paris Fashion Week, in Paris, France, July 7, 2014. The presentation of the Haute Couture collections runs from 06 to 10 July. (Photo by Etienne Laurent/EPA)

Wild weather drenches tourists, Sydney, Australia on March 7, 2017. A series of photographs as tourists take a soaking on Sydney's iconic Manly Ferry sailing big swells near Sydney's North Head. The Weather Bureau warns of large and powerful surf conditions expected to be hazardous for coastal activities such as rock fishing, swimming and surfing. (Photo by Hugh Peterswald/Pacific Press via ZUMA Wire/Rex Features/Shutterstock)