"I just got out of the river 315 miles. I'm absolutely exhausted, but also rejuvenated," Lewis Pugh, a British-South African endurance swimmer, expresses his joy after completing his latest swim that lasted 32 days and in which he covered the length of the Hudson River in New York City.

It was an arduous challenge, with his swim cap providing little protection from the rocks as he navigated the rapids. 

Despite being in the water for over a month, the swimmer says "there wasn't any time when I thought about giving up but there were some times when my shoulders were incredibly sore."

He would swim 10 miles every day, five in the morning and another five in the evening. 

'Few lights and a big blue moon'

"It was wonderful swimming at night down the Hudson because the river is so quiet and the upper sections have very few lights. There was a big blue moon and there was a very strong tide. I often just turned on to my back and above me were all the stars and the heavens and a big moon," the swimmer adds.

Pugh has been swimming for 36 years, and grew up on the coast, first in Plymouth in England and then moved to Cape Town on South Africa's southwest coast, where from his high school classroom he had a view of the ocean.

"It was just such a natural place to go, so I learned to swim when I was a young boy and I loved it," says Pugh.

The 53-year-old describes himself as a "sea water animal" and has swum all across the world in an effort to shine a light on the pollution in these areas. He has had success in urging authorities to take action to protect these areas. 

After swimming in the Antarctica a few years ago, it was his swim in the Ross Sea, a deep bay of the Southern Ocean in Antarctica, that helped raise awareness about protecting that water channel.

"It's amazing what swimming does. That area now is 1.5 million square kilometers, it's the size of Britain, France, Germany, Italy, all put together," says Pugh.

His swim in the English Channel led to the UK Environment Minister's commitment to protect 30 percent of the world's oceans by 2030. He says that since then over 130 nations have agreed to follow suit, an achievement he is proud of as the United Nations Patron of the Oceans. 

'Rivers are the arteries of our planet'

The swimmer has now expanded his focus to create awareness about keeping the world's rivers clean.

"I've only done five river swims. And the big difference, obviously, is that when you're in a river, you don't have the buoyancy of the salts which you have in the sea," says Pugh. "In rivers, you have pollution and it's much more concentrated than in the sea."

He experienced this firsthand as he swam through some sections of the Hudson River, where the pollution appeared to be a lot worse, especially after rain. 

"We get raw sewage coming into the river, so that's one of the concerns you have when swimming in a river," Pugh tells CGTN. "The rivers of the world are the arteries of our planet. We cannot have a healthy planet without healthy rivers."

He urges policymakers and individuals to think about the environment and the state they will leave the planet in for future generations, saying that everything that we pour into the rivers - such as industrial waste, agricultural runoff, plastic pollution - not only kills the river and the wildlife that inhabits it, but it then flows into the oceans and pollutes them as well.

"The rivers of the world are some of the most degraded ecosystems on this planet and they are in a very poor state," warns Pugh.

But he has been very excited about completing his swim in the Hudson and how it has given him the opportunity to tell a story about all rivers.

"At the source, you've got a beautiful wilderness area with bears and beavers and vultures and bald eagles, and towards the end of New York City there is the headquarters of the United Nations," he says as he prepares to go there to meet world leaders and deliver a message about how important it is to protect our rivers. 

"The Hudson is emblematic of all rivers, because over the past 50 years, they've made such a conscious effort to clean up this river," acknowledges Pugh, knowing that his swim would not have been possible had it not been "cleaned up mile by mile, town by town, and factory after factory. They really have transformed this river."

'We're not the only animal on this planet'

He may be exhausted, but he felt motivated to continue so he could see how hard the people have worked to clean their river. He fondly recalls how in the upper section of the river, a bald eagle flew all the way along just above him as he did a backstroke, a clear sign that the Hudson River preservation project has been successful as the species was extinct in the state just 20 years ago so seeing it has made its home here again was "beautiful."

Pugh urges New Yorkers and the world to continue to be vigilant, and not be complacent when it comes to protecting our rivers. 

"For me, protecting our rivers is an issue about justice - justice between ourselves and future generations. We must leave our rivers to our children so that they have a habitable planet, but also a justice between ourselves and the animal kingdom. These rivers are the home of the bald eagle, the sturgeon, and the black bears. We're not the only animal on this planet," he says.

He urges the youth to "lean in, protecting the planet is the defining issue of our generation."

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