Apparatus (2) for sensing at least one parameter in water, which apparatus comprises: (i) a conductivity sensor (6) for sensing conductivity in the water; (ii) a dissolved oxygen sensor (4) for sensing dissolved oxygen in the water; (iii) a glass substrate (14); and (iv) the conductivity sensor (6) and the dissolved oxygen sensor (4) are fabricated on the glass substrate (14) using photolithography and etching.