The fly has always perplexed me. It's a beautiful stroke but hard to get right. And, the more people who don't get it right, the fewer people I can watch in order to get it right. Finding someone whose stroke you can record in your head and visualize as you swim is a huge help. So, again, we turn to MP.
This video is almost 6 minutes long, has multiple angles and simply shows Phelps swimming lots and lots of fly. It's a lot more than you'd get from watching him in one of his races. The flexibility of his shoulders and upper body is absolutely remarkable. Most of us will never be like Mike, but, hopefully, just trying to emulate his stroke will have a positive influence on our own fly.