A group of men and woman are swimming.
A group of people are in a pool
People swimming are not necessarily in a pool.
exists p1 x1 x2 x3 x4.(exists x5.((x1 = x5) & n_swimming(x5)) & of(x1,x2) & n_woman(x4) & n_man(x3) & subset_of(x4,x2) & subset_of(x3,x2) & n_group(x1))
exists p1 x1 x2.(exists x3.(in(x1,x3) & n_pool(x3)) & of(x1,x2) & n_people(x2) & n_group(x1))