Don't try this at home and definitely don't try it at your local swimming pool.

Olympic swimming great Katie Ledecky has shown her balancing skills in the water are next level while partaking in a social media challenge.

The five-time Olympic gold medalist posted a video on Instagram of her completing an entire length of a swimming pool, while balancing a glass of milk on her head.

"Possibly one of the best swims of my career! (open for debate). What can you do without spilling a drop?!," she said on Instagram.