A surfer who fell off his surfboard in the ocean while trying to ride a wave.
A surfer was on a wave
Just because he was trying to ride a wave does not mean that he was on a wave.
exists e1 e2 p1 s1 x1 x2 x3 x4.(n_ocean(x4) & a_topic(x1) & while(e1,e2) & Topic(e2,p1) & Actor(e2,x2) & v_try(e2) & exists e3 x5.(Theme(e3,x5) & Actor(e3,x2) & v_ride(e3) & n_wave(x5)) & in(e1,x4) & a_off(s1) & Manner(e1,s1) & Theme(e1,x3) & Actor(e1,x2) & v_fall(e1) & n_surfboard(x3) & of(x3,x1) & n_male(x1) & (x1 = x2) & n_surfer(x1))
exists p1 x1.(exists x2.(on(x1,x2) & n_wave(x2)) & n_surfer(x1))