The state of Tennessee is seaplane friendly. The lakes are all controlled by the US Army Corps of Engineers or the Tennessee Valley Authority (TVA). Almost all lakes are open to seaplanes. TVA is a little friendlier as amphibs can use boat ramps and on the Corps lakes you can not. Some ramps are large enough for hull type amphibs such as the Lake with sponsons. One such ramp is on the north side of Lake Normandy, near Tullahoma, TN. In the winter it is deserted and no traffic at all. There are marinas on some of the lakes, some welcome seaplanes and some do not. It is best to call ahead for fuel and docking.
The rivers in Tennessee are open to seaplanes operations. Some cities consider the rivers to be in city limits and may ban prohibit seaplanes. It is best to check with the city if interested in the water within city limits. There are some cautions and distance restrictions around nuclear power plants and those are listed in the sectional charts.