a boy smiles underwater.
The boy is eating a sandwich.
You cannot be eating a sandwich while underwater.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_smile(e1) & n_underwater(x2) & n_boy(x1))
exists e1 x1 x2.(n_boy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_eat(e1) & n_sandwich(x2))