A surfboarder catches the waves.
a surfboarder in the water with a shark near by
A person can be catching a wave without a shark near by.
exists e1 x1 x2.(n_wave(x2) & Theme(e1,x2) & Actor(e1,x1) & v_catch(e1) & n_surfboarder(x1))
exists x1 x2 x3 x4.(n_water(x2) & n_thing(x1) & by(x1,x4) & n_thing(x4) & in(x1,x2) & with(x2,x3) & r_near(x3) & n_shark(x3) & n_surfboarder(x1))