A person paddles a boat on a lake.
A person is on the lake.
Just because a person paddles doesn't imply on a lake.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_paddle(e1) & on(x2,x3) & n_lake(x3) & n_boat(x2) & n_person(x1))
exists p1 x1 x2.(n_lake(x2) & on(x1,x2) & n_person(x1))