The surfer rides a wave on a blue surfboard.
the swimmer was walking on the boardwalk
If the surfer rides a wave, he is not walking.
exists e1 s1 x1 x2 x3.(n_surfer(x1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & on(x2,x3) & n_surfboard(x3) & a_blue(s1) & Theme(s1,x3) & n_wave(x2))
exists e1 x1 x2.(n_boardwalk(x2) & n_swimmer(x1) & on(e1,x2) & Actor(e1,x1) & v_walk(e1))