A man is skiing in water.
A man is skiing in water behind a jet ski
Skiing does not imply it is behind a jet ski.
exists e1 x1 x2.(in(e1,x2) & n_water(x2) & Actor(e1,x1) & v_ski(e1) & n_man(x1))
exists e1 x1 x2 x3 x4.(behind(e1,x3) & n_ski(x3) & of(x3,x4) & n_jet(x4) & in(e1,x2) & n_water(x2) & Actor(e1,x1) & v_ski(e1) & n_man(x1))