A bird flies across the water.
A bird is swimming in the water.
If the bird is swimming in water, it can't be flying.
exists e1 x1 x2.(n_water(x2) & across(e1,x2) & Actor(e1,x1) & v_fly(e1) & n_bird(x1))
exists e1 x1 x2.(n_water(x2) & in(e1,x2) & Actor(e1,x1) & v_swim(e1) & n_bird(x1))