An advocate for clean water swam through a well-known polluted waterway in Brooklyn, calling for the dirty canal to be completely cleaned so people could one day join him.

The Environmental Protection Agency (EPA) had strongly advised Christopher Swain to stay out of the Gowanus Canal, but he went in anyway Sunday morning, wearing a water-resistant suit, goggles, a swimming cap, and scuba boots. People in a boat and two kayaks accompanied Swain.

"It was cold, it smelled really bad, it freaked me out to go through some of the sewage residue and the rest of it," Swain said, in the canal fielding questions from reporters. "I ran into debris — I ran into concrete blocks."

Swain is demanding a permanent end to all sewage discharges, and said he wants a complete cleanup of the Gowanus Canal, beyond just the top layer. He said he wants the waterway to meet the standards of the Clean Water Act so it will be hygienic so anyone can swim in the waterway.

He went for a similar dip on Earth Day in 2015. Swain said his efforts are working.

"The federal cleanup really got energized by that swim and they really worked very hard to pull out that 10- to 20-foot layer of mud that sits on the canal under this water column," Swain said. "We call it black mayonnaise. Parts of it has so much coal tar residue in it that it's flammable."

Swain previously swam in other polluted New York waterways, Newtown Creek and the East River.

He said he covered his face with a non-petroleum gel and wore ear plugs, but his mouth and nose were still exposed.

Swain said he didn't swallow any of the Gowanus Canal water, but he needed to gargle hydrogen peroxide after some of it got in his mouth.

Once he got out of the canal, he dumped a bucket of water and diluted bleach solution over himself to try and kill the bacteria and virus he swam through.