an upside down man doing a flip on a waterski board
A man in a competition at the lake.
A man can do a trick on skis without being in a competition, and he could do so in bodies of water other than a lake.
exists e1 x1 x2 x3 x4 x5 x6.(a_topic(x1) & down(x1,x2) & Theme(e1,x4) & Actor(e1,x3) & v_do(e1) & on(x4,x5) & n_board(x5) & of(x5,x6) & n_waterskus(x6) & n_flip(x4) & (x2 = x3) & n_man(x2) & n_upside(x1))
exists x1 x2 x3.(n_lake(x3) & a_topic(x1) & in(x1,x2) & at(x2,x3) & n_competition(x2) & n_man(x1))