a man and woman walking across a street.
A couple is swimming.
You have to be in water to be swimming so they would not also be walking across a street.
exists s1 x1 x2 x3 x4.(a_topic(s1) & subset_of(x2,s1) & across(x2,x4) & n_street(x4) & n_walking(x2) & of(x2,x3) & n_woman(x3) & subset_of(x1,s1) & n_man(x1))
exists p1 x1.(exists x2.((x1 = x2) & n_swimming(x2)) & n_couple(x1))