If the video showed the underwater portion of her stroke, and it was compared with mine, you would have no clue that we were doing the same sport. That is one of the most dominating events I've ever seen at the world class level.
I could have raced her over the last 100m (from a dive) and I would have lost by 20 seconds.
I am a man and swam distance races for a Div. I college. (Albeit not a very competitive one).
Ledecky went through the 400 at a little faster than my PR for 400M.