A man is skiing in water.
A man is driving a boat.
He cannot be skiing at the same time as driving.
exists e1 x1 x2.(in(e1,x2) & n_water(x2) & Actor(e1,x1) & v_ski(e1) & n_man(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_drive(e1) & n_boat(x2) & n_man(x1))