British endurance swimmer Lewis Pugh completed a 315-mile (500-kilometer) journey down New York's Hudson River on Wednesday.

It took the 53-year-old a month to reach the finish line in Manhattan.

Pugh, who was appointed the first UN patron of the oceans a decade ago, undertook the marathon swim to raise awareness about the importance of clean, healthy rivers.

"Seeing the Statue of Liberty on the horizon and seeing that beautiful torch, it just made me think that every single thing which we hold dear to us depends on us being able to drink clean water and breathe fresh air and take care of our planet so that is habitable," he said.

"Rivers are the arteries of our planet."

How safe is it to swim in the Hudson River?

New York's Hudson River had long been polluted by everything from industrial chemicals to sewer runoff.

Cleanups and stricter environmental regulations have helped slowly rehabilitate the waterway in recent years.

Pugh's mission was to show the world that it's possible to undo some of the damage humans have caused by pollution.

"They're going to be inspired by what happened here and say to themselves: 'If they can do that in the Hudson, surely we can do it in our river and our river can also be saved," he said.

But the water is still not perfect. Pugh had to dodge floating plastic litter as well as tug boats as he powered through fatigue.

For some legs of the journey, he made sure to first take a swig from a bottle of Pepto-Bismol, rinse with an antiseptic mouthwash, wash with surgical soap and don ear plugs.

Pugh has previously undertaken high-profile swims in Antarctica, the North Pole and the Red Sea to advocate for rivers that are clean enough to swim and fish in.

zc/rt (AP, AFP)