People surf in the ocean.
People surf in the stormy ocean.
Not all oceans are stormy.
exists e1 x1 x2.(n_ocean(x2) & in(e1,x2) & Actor(e1,x1) & v_surf(e1) & n_people(x1))
exists e1 s1 x1 x2.(n_ocean(x2) & a_stormy(s1) & Theme(s1,x2) & in(e1,x2) & Actor(e1,x1) & v_surf(e1) & n_people(x1))