The surfer is in the wave.
a surfer riding a big wave at a competition
The surfer in the wave may not be riding it, attending a competition, and the wave itself does not have to be big.
exists p1 x1 x2.(n_wave(x2) & n_surfer(x1) & in(x1,x2))
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & at(e1,x4) & n_competition(x4) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_wave(x3) & a_big(s1) & Theme(s1,x3) & (x1 = x2) & n_surfer(x1))