That's not an easy stroke either!
A British woman named Judy Bradshaw has completed a record-setting swim around the island of Manhattan for charity.
She used the butterfly stroke the ENTIRE 28.5 miles and completed the task in 9 hours, 28 minutes, and 37 seconds.
We don't even think we could walk around Manhattan that fast!
Check out the video above to see the woman complete the amazing feat of physical endurance!