Sarah Thomas, world-record swimmer from Colorado, prepares for next challenge

Almost any day of the week, you can find Sarah Thomas in the water.

"I kind of treat Chatfield like a gigantic swimming pool," she said, referring to Chatfield Reservoir. 

Sarah has been swimming all her life, mostly in actual swimming pools as a competitive swimmer in high school and college. Then she discovered her love for open water.

"I tried the Horsetooth 10K in Fort Collins," she told CBS4's Kelly Werthmann. "I came out of the water and I was just in tears because I was so happy! It just kind of escalated from there."

That swim sent Sarah diving head first into worldwide adventure as an ultramarathon swimmer.

"I set my sights on earning my Triple Crown," said Sarah.

In swimming, the Triple Crown is earned by completing swims across the Catalina Channel (20 miles), around Manhattan Island (28.5 miles) and across the English Channel (21 miles). Sarah got her crown in 2012.

"I get out of the water in France and I kind of look back across the ocean and I was like, 'I could've kept going,'" Sarah said.

And kept going she did! Not only does Sarah have a long list of global swims on her resume, she holds a world record for the longest continuous swim done in current-neutral conditions. In 2017, Sarah swam for more than 67 hours across 104 miles in Lake Champlain.

"In that moment I was like, 'I'm not done with just the Triple Crown.' There's more out there I want to try because this was too easy," she said.

But, two months after her historic swim, things went from "too easy" to unimaginably hard.

"I was just sobbing and telling my husband I don't want to die. I'm not ready to die," said Sarah.

Just 35 years old, Sarah was diagnosed with cancer.

"When someone first says the words to you, 'You have breast cancer,'" Sarah explained with pause. "Your whole life just stops."

Yet Sarah wasn't ready to stop, despite her fears of how treatment would impact her ability to keep swimming.

"I'm going to have a mastectomy, that's going to mess up my shoulder," said Sarah.

But one year after numerous rounds of chemotherapy, doctors gave Sarah the "all clear" to get back in the water. The breast cancer survivor wasted no time beating more odds. In 2019, Sarah became the first person ever to complete four consecutive crossings of the English Channel – completing the more than 80 miles swim in just over 54 hours.

"My driving force is truly just, 'How can I meet my potential?'" explained Sarah. "Did I live my life in a way that I did everything to the best of my abilities?"

And, if you haven't guessed it by now, she's not done yet.

"There's something called the Oceans 7," said Sarah. "It's seven challenging swims pretty much on each continent."

With four down, Sarah is onto her fifth swim of the Oceans 7. In early July, she'll swim the 21-mile stretch between Northern Ireland and Scotland.

"The water in the North Channel will be in the low 50s," she said. "50 degrees is going to hurt."

That's a far cry from the 70+ degree water in Chatfield where she trains for her ultramarathon swims several days a week. Still, those bitter temps are no reason for Sarah to quit.

"There's so many things in life that make it easy to quit," she said. "Things are thrown at you and yeah, life is hard. There's always an excuse to say 'no'...or just give up on your dreams, but there's always more reasons to keep going."

Or, better yet, to just keep swimming.

"Sometimes that's your only choice. You just have to keep swimming," Sarah said.

To learn more about Sarah Thomas, as well as follow along with her upcoming swims around the globe, visit www.sarahthomasswims.com.