A group of people on a boat paddle with oars.
The rafters are going downstream
The group on the boat aren't necessarily rafters and they may or may not be going downstream.
exists x1 x2 x3 x4 x5.(a_topic(x1) & of(x1,x2) & on(x2,x3) & with(x3,x5) & n_oar(x5) & n_paddle(x3) & of(x3,x4) & n_boat(x4) & n_people(x2) & n_group(x1))
exists e1 x1 x2.(n_rafter(x1) & Theme(e1,x2) & Actor(e1,x1) & v_go(e1) & n_downstream(x2))