a clean-water activist , embarked on a 1.8-mile swim in the toxic gowanus canal , has been designated as especially polluted by the environmental protection agency , to urge its cleanup .
the swimmer , who quit two-thirds of a mile into the swim , gargled hydrogen peroxide periodically to prevent contaminated water from getting down his throat .
swain , who has previously swam the hudson and columbia rivers , said that cleanup of the gowanus canal , which was labelled as a superfund site by the epa , should be accelerated .