St. Mary's Yachting Center has undergone remodeling since its former days as Dennis Point,and it may now have floating docks. It is also close to the mouth of the Potomac. As far as floating docks, we have traveled the lower Potomac for about 14 years, and have been on the Chesapeake for the past three. Unless a marina has redone their docks, since we have been there, the only ones that I know of with floating docks is Prince William on the Occoquan, that does not accept transients, and Smallwood State Park on Mattawoman Creek, across from the Occoquan. I think Fort Washington, just north of the Occoquan may have remodeled, don't know if they have floating. Why are floating docks important to you? The tidal change is usually less than 1.5 feet on the Potomac.