PORT-AU-PRINCE, Haiti  Duquesne Fils-Aimé, stripped to the waist, stepped gingerly into the canal, drawing stares of astonishment from the spectators above. When he ducked his head under the water  if one could call it that  an audible gasp rose from the crowd.

Plastic bottles and bags, shredded underwear, shoes and endless globs of unidentifiable black muck bobbed like a fetid tarp around Mr. Fils-Aimé and his colleagues as they started another shift  cleaning out the canal by hand.

On and on they worked in the drink, making little progress but at least a little cash in a Sisyphean battle against the squalor that chokes the canals and ditches passing as sewers, causes floods of wastewater and helps spread the cholera epidemic now gripping more than half the country.

“We do the bad,” Mr. Fils-Aimé, 41, said of his work, “and maybe people won’t get sick.”

At least there were no animal carcasses that day; the men have seen plenty of them  dogs, rats, goats. They swam a few strokes, black water slopping over them in a stench many layers thick. At one point, Mr. Fils-Aimé sat entirely supported on the filth as if shipwrecked, fishing out debris to the lucky crew member on dry land.