Nothing contained herein shall be deemed to permit in a zoned residential district the docking or mooring of a commercial, charter, open party or similarly used boat or the loading or unloading of cargo or the embarking or disembarking of passengers, or to permit the sailing to or from property in such a district of a commercial, charter, open party or similarly used boat with its cargo, charter, party or passengers. For the purposes of this subsection, a "charter" or "open party" boat shall only be considered as such when embarking, disembarking or carrying passengers and/or when loading or unloading cargo or supplies.