I'll tell you what I would do......First is this an item that will be unplugged at all from the extension cord? If not, then take some silicone caulk and apply it to both parts of the connection, plug them together and tightly wrap electrical tape around the connection as to keep both parts together and keep water out. This should work for quite a while. If it is to be unplugged then I would suggest that you may have to hire an electrician to wire an outdoor GFI box near the item. Remember.."call before you dig"..ha ha..