An American woman swam across the English Channel four times in a row and set a new world record. What makes the accomplishment all the more remarkable is that Sarah Thomas is a 37-year-old breast cancer survivor who completed treatment a year ago.

Thomas, a Colorado resident who is an open-water ultra-marathon swimmer, began her swim in the early Sunday and finished Tuesday — 54 hours later. She had expected to swim a total of 80 miles, but the strong tide in the English Channel increased the distance and made her feat closer to 130 miles.

"I just can't believe we did it," Thomas told BBC News once she came ashore in Dover. "I'm really just pretty numb. There was a lot of people on the beach to meet me and wish me well and it was really nice of them, but I feel just mostly stunned."

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According to the BBC, before Thomas completed her record-breaking fourth leg, only four swimmers had ever swum three legs across the Channel without stopping. Thomas followed Channel Swimming and Piloting Federation Rules as she wore only a swim cap, goggles, and bathing suit. During her 54-hour swim, she ate only a protein mixed drink made with caffeine and electrolytes. She persisted despite being stung in the face by a jellyfish.

Lewis Pugh, a British-South African distance swimmer, took to Twitter on Tuesday to congratulate Thomas. He called her feat "superhuman!!"

Extraordinary, amazing, super-human!!! Just when we think we’ve reached the limit of human endurance, someone shatters the records. Huge congratulations to Sarah Thomas on swimming the English Channel 4x continuously!!! 🏴󠁧󠁢󠁥󠁮󠁧󠁿🏊‍♀️🇫🇷 🏊‍♀️🏴󠁧󠁢󠁥󠁮󠁧󠁿🏊‍♀️🇫🇷🏊‍♀️🏴󠁧󠁢󠁥󠁮󠁧󠁿 pic.twitter.com/kOa9QlereH — Lewis Pugh (@LewisPugh) September 17, 2019

Thomas completed her record-breaking swim across the English Channel to raise awareness for breast cancer. She dedicated her swim to other survivors. When she arrived on land, Thomas ate M&M's and took a sip of champagne, though she said it was difficult to swallow because all of the salt water had affected her mouth.

BBC News reports Thomas is an experienced open-water swimmer who completed her first event in 2007. She first swam across the Channel in 2012 and once more in 2016.