Activist swims the Newtown Creek

NEW YORK (FOX5NY.COM) - A three-and-a-half mile, nearly three-hour swim through one of the most heavily polluted bodies of waters in the country can leave you feeling gross.

"This is definitely the worst thing I've done in 20 years," said swimmer and clean water advocate Christopher Swain. He has plunged into dozens of polluted waters to raise awareness of the need for action, including the nearby Gowanus Canal. But he says the combination of sewage runoff and toxic oil in Newtown Creek was uniquely disgusting, especially the smell.

"Poop, the smell of like chemicals that smelled like cinnamon toast, the fumes from gas and oil and there were some sulfur type of smells, too," he said. "I was ready for the gas and oil. I wasn't ready for as much of the visual reminders of the sewage as I got."

Newtown Creek is the site of one of the largest oil spills in United States history; between 17 million and 30 million gallons of oil have leaked into the soil from processing facilities surrounding the water.

In 2010 the area was granted Superfund status by the Environmental Protection Agency, which promised a comprehensive cleanup. The creek is also home to the city's largest wastewater treatment plant, which Swain said only complicates the cleanup.

"Every time you flush a toilet in Lower Manhattan that gets piped to the Newtown Creek waste water treatment plant and when it's raining, they can't handle the load -- and it goes right in here and I swim right through it," he said. "We need to fix that."

During the swim, Swain collected samples he plans to share with science teachers.

Curious onlookers give him credit for his dirty work.

"I'm willing to freeze. I'm willing to swim in poop because I think unless someone puts themselves on the line, nothing changes," he said.

Swain isn't done with Newtown Creek yet. The creek actually has five estuaries. Swain only swam one on Wednesday and he plans to come back in January to complete the rest.