Katie Ledecky is a rockstar in the pool and famous not just for usually beating her opponents but also for the way she absolutely dominates them, sometimes finishing a race several body lengths ahead of second place.

But as it turns out, the five-time Olympic gold medalist can perform at least one truly astonishing trick in the pool too.

Monday on Instagram, Ledecky posted a video of herself swimming one length of the pool (likely 50 meters but possibly 50 yards). No big deal, right?

The catch was she had a cup of chocolate milk balancing...