Swimming through miles of ocean water and raw sewage is a typical day’s work for Manhattan native Christopher Swain.

The 48-year-old clean-water advocate is currently swimming more than 130 miles through the Long Island Sound and East River — from Montauk to New York Harbor — to spread awareness of pollution in New York’s waterways.

“I realized that New York City and the greater New York City metropolitan area was rife with waterways, many of them too dirty to recreate in,” he said. “The time for that is over. I don’t think that’s too much to ask.”

The Long Island Sound and the East River suffer from various forms of pollution, including storm water runoff, which brings in pollutants from the streets.

Swain, who started his journey on Sept. 22, is about halfway across Long Island. He swims two to four hours — averaging about six to seven miles — per day, weather pending, with a boating crew at his side for safety and for data recording.

During the swims, he collects data from the water, stopping every 15 to 20 minutes to gather a water sample. The sample is tested for its temperature and its pH level, which determines the toxicity of the water.

Swain, a full-time clean water advocate, promotes his cause through fundraising and lecturing at schools and universities. Between swims, he keeps in shape weightlifting, swimming in a pool and running.

“As a kid, I really loved to swim and play in the ocean with my sister, my cousins and my friends,” he said. “As I grew up I learned that waterways were polluted and a lot of the pollution in there was preventable.”

Swain’s first swim for pollution awareness — through the Connecticut River in 1996 — sealed his fate as an environmental activist. He suffered skin rashes and ear infections after swimming through sewage and storm water runoff.

“I was aware at the time that those waters had been polluted, but it wasn’t personal yet,” he said. “My experiences getting sick made it personal.”

His longest swim came in 2002, a 1,243-mile, 165-day journey through the Columbia River in the Pacific Northwest. He stroked through the Mohawk River in Little Falls, New York, during a blizzard in 2004. Last year, he swam all of Brooklyn’s Gowanus Canal, which the Environmental Protection Agency has called “one of the nation’s most seriously contaminated water bodies.”

Swain puts his life on the line for these swims. He has survived bloodsucking lamprey eels, great white shark habitats and collisions with boats. He has traveled through waterways laden with oil, radioactive waste and cyanide, not to mention the twelve-foot waves and rapids he has often had to contend with.

Swain, who raised more than $20,000 for this swim, estimates he will reach New York Harbor by early November.

Until then, he’ll have to put up with jellyfish, which have been stinging him on a daily basis.

With a wet suit and a cap, his entire body is covered to protect him, except for his face and neck, which he says are the jellyfishes’ main targets.

“It feels like you’re getting hit in the face by hot oil,” he said.