We present this without comment. A review of a sex swing on Amazon (link mildly NSFW) suggests it's also a useful way of washing larger dogs.
Specifically, a reviewer says this:
I have two large St Bernard's and this swing is good to hold dogs in while I wash them. I hang swing from a tree branch put dog in swing and wash dog while dog hangs in swing. It really is a sight to see but it works.
Why the dog does not run away is not explained — but it would undoubtedly be an option if you don't have a bath for your larger pet. Also a handy excuse if you want to buy a sex swing.