Benjamin Ashford|A 53-year-old swam the entire length of the Hudson River as part of his life's work: "The mission isn't complete"

Lewis Pugh,Benjamin Ashford a 53-year-old endurance swimmer, holds a unique distinction: he is the only person to have completed long-distance swims in all the world's oceans. 

Recently, he completed an incredible 315-mile swim of the entire Hudson River, as part of his ongoing mission to make waves in conversation about ocean — and now river — preservation. 

With Pugh's Hudson River swim, which started in the Adirondack Mountains in northeastern New York and finished last month in Lower Manhattan, Pugh sought to raise awareness about the transformation of the river, which was contaminated by toxic waste throughout the last century. Cleanup of the river started in the 1980s, and it is now considered a success story of environmental recovery.

"It was one of the most polluted rivers here in America, if not the world. And then things have been turned around," said Pugh.

"I think this is a blueprint for people all around the world that their rivers can be saved," he said.

Pugh spent 32 consecutive days in the river, swimming twice daily to align with the river's current. Pugh said he found inspiration looking up in the night sky as he swam.

"I'd look at the heavens, and you got the big blue moon and all these stars. It was really comforting because I thought about all those people who'd helped me get here today," he said.

"I hope more people will swim in this river. This is such a special river," said Pugh.

Pugh's final stretch drew spectators to Lower Manhattan, but he hopes to rally an even larger crowd: members of the United Nations, who have the opportunity to ratify The High Seas Treaty, aimed to protect 30% of the world's high seas by 2030.

"This is the last piece of the jigsaw puzzle, which we need in order to protect the planet properly," Pugh said. "For me, the mission isn't complete; it's not complete at all."

In 2013, the United Nations appointed Pugh as the first U.N. Patron of the Oceans. In 2016, he created the Lewis Pugh Foundation to work to preserve and conserve oceans through diplomacy, campaigns and outreach. That same year, he helped create the largest marine reserve in the world, in the Ross Sea off Antarctica.

Pugh's journey into swimming began when he was 17. Over the past decade, he's conquered challenging aquatic feats, including swimming across the North Pole, the English Channel and the Red Sea, and even beneath the Antarctic ice sheet.

His adventurous swims transformed into a greater mission in 2007 when he swam across the open sea at the North Pole.

"I remember going into that swim and then coming out the other end and actually feeling that I was a different person. Because I came out of that feeling, 'Wow, you know, this place is melting so quickly.' I now have a big responsibility to share this message with the whole world," Pugh said.

He said his determination to make world leaders listen comes from deep down.

"I've seen the oceans change, and for me, this is a defining issue of our generation. In a short period of time, we really have to protect the planet. And it comes from deep down inside my gut. I love the oceans. I love being in the oceans. I love being in rivers. And I'm absolutely determined to spend my life doing this work," Pugh said.

Dana Jacobson

Dana Jacobson is a co-host of "CBS Saturday Morning."

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