There are some places where the water is so cold and/or brackish that growth might not be too bad, but almost anywhere on the East Coast you would regret not putting on bottom paint. Over decades of cruising I have tried many different paints and by far the best have been the traditional, old-style, hard paints like Trinidad, especially the black color for some reason. Some of the tougher ablatives, like Petit's ACP50 weren't too bad, but not up to Trinidad. We used to be able to leave our boat in Florida for months at a time and still not have a problem except for the prop which would be a solid ball of barnacles when we returned. Nothing beats a heavy load of copper and a hard paint that can be scrubbed when you're in the water for antifouling properties. When you used to be able to get TBT in paint it was even better, but that has now been outlawed.