Multiple people in a swimming pool.
A group of people are playing water polo in a pool.
Not all people in a swimming pool are playing water polo.
exists x1 x2 x3 x4.(a_topic(x1) & in(x1,x3) & n_pool(x3) & of(x3,x4) & n_swimming(x4) & n_people(x1) & (x1 = x2) & ne_nam_multiple(x2))
exists e1 x1 x2 x3 x4 x5.(in(e1,x5) & n_pool(x5) & Theme(e1,x3) & Actor(e1,x1) & v_play(e1) & n_polo(x3) & of(x3,x4) & n_water(x4) & of(x1,x2) & n_people(x2) & n_group(x1))