Atlantic Ocean Atlantic Ocean

The Greenland ice sheet, the second largest body of ice in the world which covers roughly 80 percent of the country, has been melting and its glaciers retreating at an accelerated pace in recent years due to warmer temperatures. David Goldman/AP hide caption

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David Goldman/AP

Chris Bertish enters the English Harbour at Antigua on Thursday, a flare trailing behind him in celebration. He paddled more than 4,050 nautical miles to reach this point. Courtesy Brian Overfelt for The SUP Crossing hide caption

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Courtesy Brian Overfelt for The SUP Crossing

South African surfer and sailor Chris Bertish practices in his 20-foot stand-up paddleboard, just days prior to his launch on Tuesday. Alan van Gysen/Courtesy of The SUP Crossing hide caption

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Alan van Gysen/Courtesy of The SUP Crossing

American surfer Garrett "GMAC" McNamara rides what could be, if confirmed, the biggest wave conquered in history as a crowd watches Monday in Nazare, Portugal. To Mane/Barcroft Media /Landov hide caption

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To Mane/Barcroft Media /Landov