Jim - we keep our boat about twenty miles south of DC on the Occoquan. We've never had to have anyone dive on our boat. It is fresh water (not even brackish) and the only fouling we have experience with two boats over the past ten years is slime. Once you get south of the 301 bridge and the water starts to turn brackish, all the slime will die and fall off in a few days. Nathan Carolena II Nordic Tug 34 Washington, DC