An environmental activist who swims through sewage spills, shark habitats, and shipping lanes in order to "put our waterways squarely in the public eye" took a particularly disgusting dip on Earth Day this year: in the Gowanus Canal in Brooklyn, known as one of the most polluted bodies of water in the United States.

Christopher Swain, 47, wore a yellow-and-black protective suit, gloves, goggles, and a green swim cap on which he wrote, in black marker, '#HOPE'—and employed what he described as a "modified head-up grandma breaststroke"—to swim about two-thirds of the murky canal on Wednesday.

According to the New York Times, he also plugged his ears and rubbed the exposed skin on his head with a water-repellent lubricant. A volunteer kayaker paddled a few feet away from him, holding a bottle of hydrogen peroxide for him to gargle with whenever his unprotected mouth strayed too close to danger.

That was smart. Since the 19th century, industrial and sewage waste has been spewed into the waterway. As the Times notes, "A 2012 report compiled by the city's Department of Environmental Protection found that the toxic chemicals in the water included copper, lead, mercury, carcinogenic PCBs, DDT and other substances. The water also teems with bacteria and viruses that, depending on the strength of one's immune system, could incite a case of nothing, mild diarrhea, dysentery or worse."

Not surprising, then, that "it tasted like mud, poop, ground-up grass, and gasoline," as Swain told a group of reporters after the swim.

The Environmental Protection Agency has designated the canal, once a major transportation route, a federal Superfund site. Clean-up efforts, which are projected to cost about half a billion dollars, are slated for completion in 2022.

Acknowledging that those working on the clean-up are "actually getting somewhere," Swain remains hopeful that the Canal will someday be swimmable—even without protective gear.

"We put a man on the moon. We split the atom," he said. "We can clean up the Gowanus Canal."

The Brooklyn Daily Eagle created a video about Swain's swim: