A father and son working on a boat.
person walking on river side
There are two people working on a boat, not just one person walking on the shore.
exists e1 s1 x1 x2 x3 x4.(a_topic(s1) & subset_of(x2,s1) & on(e1,x4) & n_boat(x4) & Actor(e1,x3) & v_work(e1) & (x2 = x3) & n_son(x2) & subset_of(x1,s1) & n_father(x1))
exists x1 x2 x3 x4.(a_topic(x1) & on(x1,x3) & n_side(x3) & of(x3,x4) & n_river(x4) & Time(x1,x2) & n_walking(x2) & n_person(x1))