People gather as a crowd of sea lions lay on floating docks at Pier 39 in San Francisco, California May 4, 2015. Hundreds of sea lions began hauling out on the docks following the Loma Prieta earthquake of 1989, and face no natural predators at the pier. (Photo by Robert Galbraith/Reuters)

In this May 8, 2015 photo, sisters Zoraida Infante, left, and Graciela Trujillo pray on Fishermen's Beach before therapeutic swimming in the Pacific Ocean in Lima, Peru. Under overcast skies, the bathers practice thalassotherapy, which derives from the Greek “thalasso”, for “sea”, and draws on the ocean's healing properties. (Photo by Rodrigo Abd/AP Photo)

More than 700 underwater images were submitted for the 2012 Annual Underwater Photography Contest, hosted by the University of Miami's Rosenstiel School of Marine & Atmospheric Science. This year, for the first time, the University of Miami set up a “Fan Favorite” category for its underwater photo competition. Internet users could vote for their favorite among five pictures. Todd Aki's photo of a jellyfish took the prize, snaring 599 of the 1,221 votes cast. (Photo by Todd Aki)

Brian Skerry can be called many things – explorer, journalist, conservation advocate – but he is first and foremost a photographer. His journeys to capture amazing underwater photographs have taken him across the world’s oceans. Photo: This Bahamian oceanic whitetip shark, known for the distinctive coloring on its white-tipped, rounded extremities, is part of a globally threatened species due to overfishing demands, primarily for its fins. (Photo by Brian Skerry)

This undated handout photo received from the Antarctic Ocean Alliance on October 28, 2016 shows a adelie penguin jumping onto the ice in the Ross Sea in Antarctica. The world's largest marine reserve aimed at protecting the pristine wilderness of Antarctica will be created after a “momentous” agreement was finally reached on October 28, 2016 with Russia dropping its long-held opposition. (Photo by John Weller/AFP Photo/Antarctic Ocean Alliance)

The Sculpture Bank (2017) by Chinese artist Mu Boyan is exhibited along the Bondi to Tamarama Coastal walk as part of the Sculpture by the Sea exhibition in Sydney, Australia, October 18, 2018. (Photo by Charlotte Curd/The Guardian)

A squid in the Red Sea. Underwater photographer Andrey Nekrasov, 42, photographed bigfin reef squid in the pitch black Red Sea putting on an extraordinary light show when the sun goes down. (Photo by Andrey Nekrasov/Medavia/ABACAPress)