Teeming with images of spectacular underwater scenes from around the world, Call of the Blue is the culmination of a five-year project by the photographer and ocean conservationist Philip Hamilton. This groundbreaking book includes contributions from acclaimed scientists and ocean “guardians”, who reveal what drove them to answer the call of the blue. (Photo by Philip Hamilton/The Guardian)

A newlywed couple dangling from a cliff face poses for wedding photos at the Chaya Mountain scenic spot on November 11, 2017 in Zhumadian, Henan Province of China. Chaya Mountain scenic spot was the shooting place for TV series “Journey to the West” and working staff dressed as main characters in this TV series to send the blessing to the newly-weds. (Photo by Sipa Asia/Rex Features/Shutterstock)

A Kurdish female fighter from the People's Protection Units (YPG) gestures as she carries her weapon near al-Hawl area where fighting between Islamic State fighters and fighters from Democratic Forces of Syria are taking place in south-eastern city of Hasaka, Syria November 10, 2015. (Photo by Rodi Said/Reuters)

The Mexico – United States barrier – also known in the United States as the border fence, rotted fence or border wall – is actually several separation barriers designed to prevent illegal movement across the Mexico – United States border.

A large stainless steel shovel lies on top of steamed crabs at the A.E. Phillips & Son Inc. crab picking house on Hooper's Island in Fishing Creek, Maryland August 26, 2015. Workers speed through the lump and back fin meat inside the crabs while leaving the more tedious task of picking the claws to others. (Photo by Jonathan Ernst/Reuters)

The blue-footed booby (Sula nebouxii) is a marine bird in the family Sulidae, which includes ten species of long-winged seabirds. Blue-footed boobies belong to the genus Sula, which comprises six species of boobies. It is easily recognizable by its distinctive bright blue feet, which is a sexually selected trait. Males display their feet in an elaborate mating ritual by lifting their feet up and down while strutting before the female.