Boy enjoys a day on the lake.
A boy is in a canoe on a lake.
The boy is on a lake but he isn't necessarily in a canoe.
exists e1 x1 x2 x3.(n_lake(x3) & ne_nam_boy(x1) & on(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_enjoy(e1) & n_day(x2))
exists p1 x1.(exists x2 x3.(in(x1,x2) & on(x2,x3) & n_lake(x3) & n_canoe(x2)) & n_boy(x1))