A plane is taxiing next to some water
The plane is on a runway.
Just because the plane is next to some water doesn't mean it is on a runway.
exists e1 x1 x2.(to(e1,x2) & n_water(x2) & r_next(e1) & Actor(e1,x1) & v_taxi(e1) & n_plane(x1))
exists p1 x1.(n_plane(x1) & exists x2.(on(x1,x2) & n_runway(x2)))