(a) All streams or other bodies of water which appear as lines, to indicate natural waters, on the reference maps herein, and which are not specifically designated in Table I, shall be assigned the same classes and standards of quality and purity as the specifically designated waters to which they are directly tributary.

(b) All streams, ponds, estuaries or other bodies of water which are not shown on the reference maps herein shall be assigned to Class D, as set forth in Part 701, supra, except that any continuous flowing natural stream which is not shown on the reference maps shall have the same classification and assigned standards as the waters to which it is directly tributary; or, if they be tidal salt waters, such waters which are not shown on the reference maps herein shall be assigned to Class SD, as set forth in Part 701, supra, except that any continuous flowing natural stream which is not shown on the reference maps shall have the same classification and assigned standards as the waters to which it is directly tributary.