The water is very clear.
The water is not polluted.
not polluted is the same as . clear.
exists s1 x1.(n_water(x1) & r_very(s1) & Theme(s1,x1) & a_clear(s1))
exists x1.(n_water(x1) & -exists e1.(Theme(e1,x1) & v_pollute(e1)))