All of Katie Ledecky’s races at the 2015 FINA World Championship are available on the Universal Sports’ YouTube channel.
This is a shorter edited video of Ledecky's amazing 1500m world record freestyle performance:
https://www.youtube.com/watch?v=GDKyTGGMT4Q
When you watch the video, it looks like Ledecky is swimming by herself since there’s no other swimmers near her.