All watercraft less than 12 feet in length, including row boats, canoes, personal watercraft, jet skis, sail boats and other such watercraft, shall be exempt from the provisions of this section when located in the R-75, R-50, R-40A, R-40B, R-40E, R-40W, R-B-1, R-B-2, R-B-3, R-B-4, R-B-5, R-B-6, and R-B-7 Zones.