There are TONS of secret swimming holes in Nashville! One of them is along the Harpeth River in Franklin (near the intersection of Temple Road and Old Natchez Trace) AND it has a rope swing!
However, it's hard to find information about since it's just a swing that people have found over the years and remember to go back to! There are a bunch of these swimming hole/rope swing locations along the Harpeth River!
Read more about it here. & if you go check it out, make sure to be safe!