TORONTO — A British swimmer who says he wants to wake up politicians around the world to the threat of climate change has successfully completed a kilometre-long swim in the freezing water of the North Pole.

Lewis Gordon Pugh swam Sunday for 18 minutes and 50 seconds in temperatures of minus 1.8 degrees Celsius in just Speedo briefs, cap and goggles.

"I am obviously ecstatic to have succeeded but this swim is a triumph and a tragedy,'' the 37-year-old British lawyer said after coming out of the water.

"A triumph that I could swim in such ferocious conditions but a tragedy that it's possible to swim at the North Pole.''

Pugh said he hoped that his swim will make world leaders take climate change seriously.

"The decisions which they make over the next few years will determine the biodiversity of our world,'' he said.

"I want my children, and their children, to know that polar bears are still living in the Arctic -- these creatures are on the front line up here.''

Swimming has given him a unique perspective on climate change, Pugh says on his website.

"I have witnessed retreating glaciers, decreasing sea ice, coral bleaching, severe droughts and the migration of animals to colder climates.''

"It's as a result of these experiences that I am determined to do my bit to raise awareness about the fragility of our environment and to encourage everyone to take action.''

Training for the challenge in northern Norway, Pugh said last month that he would place the flags of 10 countries at 100-metre intervals in the snow alongside his path through the water, representing the homes of the people on his team. The fifth flag would be Canada's.

"Canada is so important to me. Your government has sort of lurched away from the environment a little bit. It's a dream to try to get my message in to Canada,'' Pugh said in June.

Calling it the hardest swim of his life, Pugh said Sunday that the water was black when he jumped in.

"It was like jumping into a dark black hole.  It was frightening. The pain was immediate and felt like my body was on fire,'' said Pugh, who's an ambassador for the World Wildlife Fund UK.

"I was in excruciating pain from beginning to end and I nearly quit on a few occasions.''

Colin Butfield of WWF UK called the challenge "a bitter sweet victory, as this swim has only been possible because of climate change.''

Pugh is known for his epic swims in waters from the Antarctic to the Indian Ocean.