In this May 2016 photo released by The Ocean Agency/XL Catlin Seaview Survey, a boat sails near a coral reef that has been bleached white by heat stress in the Maldives. oral reefs, unique underwater ecosystems that sustain a quarter of the world's marine species and half a billion people, are dying on an unprecedented scale. Scientists are racing to prevent a complete wipeout within decades. (Photo by The Ocean Agency/XL Catlin Seaview Survey via AP Photo)

Museum employee Victoria views a giant grouper fish specimen at the Natural History Museum in west London March 25, 2015. It forms part of a new exhibition, “Coral Reefs: Secret Cities of the Sea”, featuring a panoramic virtual dive and over 250 specimens from the Museum's coral, fish and marine invertebrate collection, which opens on March 27. (Photo by Toby Melville/Reuters)

Photographer Mark Tipple captured the underwater pictures with his friend Mike as the surfer. But the rough waves of the coast of the Cook Islands slammed Mike into the sea bed during the shoot, causing him to slice his skin open and badly bruise his body. Photo: Mike diving beneath a shallow wave. (Photo by Mark Tipple/Caters News Agency)