"Admiralty Head Marine Preserve" is defined as waters and bedlands inside a line beginning at the extreme low water line on the west shore of Whidbey Island at 48°09.46'N, 122°40.88'W then northerly along the extreme low water line for 0.6 nautical miles, then due west 400 yards, then southerly parallel to the shore to a point due west of the point of origin, then due east to the point of origin.