First off, I would move the boat if possible. Then I would get some professional type bait/poison. You want to get something that the ants take back to their main nest that will eventually kill the colony. If you just spread some kind of repellent around, they will figure out how to get around it and they will keep coming back. The stuff at Lowes doesn't work well, as most of their stuff is repellent type. There is an on-line company called "Do My Own Pest Control" that sells various products that are good. I had a lake place that had carpenter ants and I finally got rid of them, but it took some effort. Good luck!