The man and woman are sitting by the boats.
A couple is sitting by the boats waiting for the captain.
Not every man and woman is a couple. Not everyone sitting by boats is waiting for the captain.
exists e1 x1 x2 x3 x4.(n_boat(x4) & n_woman(x3) & n_man(x2) & subset_of(x3,x1) & subset_of(x2,x1) & by(e1,x4) & Actor(e1,x1) & v_sit(e1))
exists e2 e1 x1 x2 x3.(n_captain(x3) & n_boat(x2) & for(e1,e2) & for(e2,x3) & Actor(e2,x1) & v_wait(e2) & by(e1,x2) & Actor(e1,x1) & v_sit(e1) & n_couple(x1))