A black dog is retrieving a ball in water.
A dog swimming back to the beach.
Just because a dog is swimming back to the beach doesn't mean it retrieved a ball.
exists e1 s1 x1 x2 x3.(in(e1,x3) & n_water(x3) & Theme(e1,x2) & Actor(e1,x1) & v_retrieve(e1) & n_ball(x2) & n_dog(x1) & a_black(s1) & Theme(s1,x1))
exists x1 x2 x3 x4.(n_beach(x4) & a_topic(x1) & to(x3,x4) & back(x1,x3) & n_thing(x3) & n_swimming(x1) & of(x1,x2) & n_dog(x2))