A man on a surfboard is surfing, while a large wave is crashing.
a man surfing
A man who is surfing does just that.
exists e1 p1 x1 x2.(exists e2 s1 x3.(Actor(e2,x3) & v_crash(e2) & n_wave(x3) & a_large(s1) & Theme(s1,x3)) & while(e1,p1) & Actor(e1,x1) & v_surf(e1) & on(x1,x2) & n_surfboard(x2) & n_man(x1))
exists x1 x2.(a_topic(x1) & n_surfing(x1) & of(x1,x2) & n_man(x2))