a boy smiles underwater.
The boy is a swimmer.
underwater   doesn't always mean swimmer.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_smile(e1) & n_underwater(x2) & n_boy(x1))
exists p1 x1.(n_boy(x1) & exists x2.((x1 = x2) & n_swimmer(x2)))