A Hawaiian cleaner wrasse provides its cleaning services to a yellowfin goatfish in a reef community off the Big Island in Hawaii. Cleaner species help rid their hosts of ectoparasites, dead tissue, bacteria and fungi. Studies have shown cleaning to play a vital role in keeping many reef ecosystems healthy. (Photo by Marty Snyderman/Caters News Agency)

Security personnel patrol around West Lake in Hangzhou, Zhejiang Province, China, August 31, 2016. (Photo by Reuters/Stringer)

A migrant labourer brushes his teeth in front of a scrapped helicopter model in Mumbai, India, April 13, 2016. (Photo by Danish Siddiqui/Reuters)

Japanese chorus girls appear to be drilling in military tactics atop their theater building as they perform salutes, June 30, 1937. The officer is from the Japanese regular army and says the girls display more rhythm in their drills than do the regular troops. (Photo by AP Photo)

Actors perform in a scene during the “Dino Safari” show in Tokyo, Japan, 25 April 2018. The Dino Safari show features dinosaurs moving in a realistic way thanks to the Dino-Tronics mechanism that enable the dinosaurs to walk, move their heads and jaws. The event will run from 26 April to 05 May 2018. (Photo by Franck Robichon/EPA/EFE)

The Invasion. A quiet street in Macau. Modernization around is quickly changing the city, as documented by Paul Tsui. (Photo by Paul Tsui/National Geographic Travel Photographer of the Year Contest)

A grey seal basks under a rainbow on a beach on the Lincolnshire coast, England on November 21, 2017. (Photo by Sean Weekly/Caters News Agency)

Novice DSLR (Digital single-lens reflex camera), 2nd Place. “Smile of a Friend”, American Crocodile (Crocodylus acutus) in Jucaro, Cuba. (Photo by Antonio Pastrana/The Ocean Art 2018 Underwater Photography Competition)