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Call it a doodoo over!

Do-gooding daredevil Christopher Swain — who in April made an abortive attempt to swim the entire Gownus Canal — will risk life, limb, and hygiene for a second time on Saturday, when he takes another stab at traversing the full length of America’s foulest cesspool.

“I’m going to finish it,” said Swain. “We’re totally hoping to get to the end of this.”

Swain garnered national media attention for his first attempt to breast-stroke his way up the Superfund site — which has served as the borough’s de-facto sewage runoff and toxic-waste dump since the 19th century — to call attention to the slow-moving federal cleanup of the waterway.

But when rain clouds loomed about two-thirds of a mile into the nearly two-mile-long canal — threatening to unleash thousands of gallons of human waste into the waters — Swain high-tailed it out of there.

Afterwards, King’s County’s toxic avenger vowed that he would one day conquer the canal — and that day could very well be Oct. 17.

For his redemption swim, Swain will once again don his combination of dive gear and hazardous-materials suit to protect him from Brooklyn’s nautical purgatory, which is riddled with various heavy metals, Coney Island Whitefish, gonorrhea, and a 10-to-15-foot base of sludgy, mercury-laden “black mayonnaise.”

His mouth, however, will be vulnerable to the toxic waters, and he will be forced to gargle with hydrogen peroxide if any of the liquid gets into his mouth, or swallow charcoal tablets if — God help him — he swallows it, he said.

“That’s the one weak point of the system, water’s going to get in my mouth,” Swain said.

He will also employ a style of swimming pioneered by grandmas everywhere — a sort of breast-stroke in which he leans his head back to keep it as far from the canals noxious current as possible.

“I realize they were doing it to protect their hair, but if your goal is to keep you head over the water, they were actually onto something,” said Swain, who has also paddled the 315-mile length of the Hudson River. “So I’ve adopted this for polluted waterways.”

The Environmental Protection Agency is once again urging Swain to stay out of the water, but Swain says he is not deterred — and he wants to show the feds what it means to get the job done.

“I don’t want to do a partial swim anymore than I want to see a partial cleanup,” said Swain. “I want to keep my promise, but I also want to finish the cleanup.”

Go cheer Christopher Swain as he takes off near the Union Street Bridge (Union Street between Bond and Nevins streets in Gowanus). Oct. 17 at 10:30 am. Free.