Snorkellers approach an adult manatee at Three Sisters Spring, Crystal River, Florida. You might imagine that coming face to face with one of these enormous underwater mammals would cause some concern. However, the likelihood is that the rotund creature just wants you to scratch its belly while it floats around happily, as world-renowned underwater photographer Alex Mustard discovered. (Photo by Alexander Mustard/Barcroft Media)

In this Wednesday, March 18, 2015 photo, limestone quarry workers walk through a cloud of dust spewed into the air by rotor blades of the stone-cutting machinery in the desert of Minya, southern Egypt. Around 45,000 people, including children, work in an estimated 1,500 quarries, digging out stones that later will be used in construction or powdered to be used by pharmaceutical and ceramic companies. (Photo by Mosa'ab Elshamy/AP Photo)

Galapagos – Rocking the Cradle: Four major ocean currents converge along the Galapagos archipelago, creating the conditions for an extraordinary diversity of animal life, April 25, 2016. The islands are home to at least 7,000 flora and fauna species, of which 97 percent of the reptiles, 80 percent of the land birds, 50 percent of the insects and 30 percent of the plants are endemic. (Photo by Thomas P. Peschak for National Geographic/World Press Photo)

A Maori soldier runs as New Zealand's soldiers march down the Champs Elysees in Paris during a rehearsal of the annual Bastille Day military parade on July 12, 2016. (Photo by Thomas Samson/AFP Photo)

Rabbits are seen in a cage, which is placed by authority as a test of the living conditions near the site of last week's blasts at Binhai new district in Tianjin, China, August 19, 2015. According to local media, the animals were alive after being placed near the blasts site for two hours. Four new fires have broken out at the site where two huge blasts last week killed 116 people, Chinese state media reported Friday soon after officials said safety hazards were found at almost 70 percent of firms handling dangerous chemicals in Beijing. (Photo by Reuters/Stringer)

In collaboration with the Pennsylvania Department of Transportation, Allegheny College art students repurpose used street signs as art materials to create the PennDOT Road Sign Sculpture Garden in Meadville, Pennsylvania, USA on August 19, 2017. (Photo by Brian Cahn/ZUMA Wire/Rex Features/Shutterstock)

Sally Rand dances on a beach in St. Petersburg, Florida, February 17, 1936. (Photo by AP Photo)

People slide down a 1,082 feet (330 metre) long inflatable water slide in Hong Kong, China August 22, 2015. (Photo by Tyrone Siu/Reuters)