The surfer is riding a wave back towards the beach.
There are no waves at the beach.
A surfer cannot be riding a wave back towards the beach if there are no waves at the beach.
exists e1 s1 x1 x2 x3.(n_beach(x3) & n_surfer(x1) & towards(e1,x3) & a_back(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_wave(x2))
exists p1 x1 x3.(n_beach(x3) & -exists x2.((x1 = x2) & at(x2,x3) & n_wave(x2)))