Kids are playing in the sand.
Kids are swimming.
They cannot be in the sand and swimming simultaneously.
exists e1 x1 x2.(n_sand(x2) & in(e1,x2) & Actor(e1,x1) & v_play(e1) & n_kid(x1))
exists e1 x1.(Actor(e1,x1) & v_swim(e1) & n_kid(x1))