Sarah Thomas started swimming in the dark. At midnight, the beginning of Sunday, September 15, she entered the English Channel from Samphire Hoe Beach in England, wearing a swimsuit, goggles, and swim cap. Her body was greased with lanolin to keep from chafing; Desitin, typically used for diaper rash, was spread like paint across her arms, back, chest, and face to protect her from the sun when it finally rose. Earplugs to keep seawater out muffled all sounds.

Ahead, the boat that would guide her to France and back hovered in the water, its lights casting a glow around the silhouettes of her support crew.

Thomas raised her arm to signal that she was ready and plunged into the Channel. She didn’t get out of the water for 54 hours, when she finished her swim on Tuesday, September 17. By then, she’d swum through three sunrises and two sunsets, and she’d done what no one else had ever done: swum 84 miles across the English Channel four times, nonstop.

This is not the first record Thomas has set. Since her first open water swim in 2007, the 37-year-old Conifer resident has made a name for herself swimming distances that require her to stay up multiple nights, following the maxim of Pixar’s Dory: Just keep swimming. In 2013, she was the first person to swim down and back across Lake Tahoe. In 2016, she swam 80 miles in Lake Powell (between Utah and Arizona), breaking the record at the time for the longest swim in a current-neutral body of water. In August 2017, she swam 104 miles in Lake Champlain over about 67 hours, her longest swim to date.

Prior to Champlain, she scheduled this fall’s English Channel swim (Thomas says the wait list for an official Channel swim is often two years). She’d set her sights on becoming the first person to swim across it four consecutive times. Then, three months after swimming Champlain, Thomas was diagnosed with breast cancer.

For most of Sarah Thomas’ swim, no land was in sight. Photo by Jon Washer

“I had planned [to use] all of 2018 to do other long swims to prepare me for the English Channel, but I got to do cancer treatment instead,” she says.

She had stage two triple negative breast cancer, which does not respond to hormone treatments. There were two tumors in her right breast and one in a lymph node. Between her November 2017 diagnosis and August 2018, she went through chemotherapy—which successfully killed everything—a mastectomy, and radiation treatment.

She swam as much as she could during her treatment, but immediately after her mastectomy and during radiation, Thomas found herself stuck on dry land. Her surgery caused immobility in her shoulders. She lost a lot of strength.

When she swam the annual 10k at Horsetooth Reservoir in Larimer County last September, she struggled to finish the normally easy distance and was exhausted for days afterward. The swim served as a reality check and a benchmark. She had about a year to train for the Channel, and a lot of water to cover.

Throughout September and October, she fought to regain her strength. By December, she says she finally felt like herself. In March, she swam the Cook Strait in New Zealand to gauge her physical condition, and after a quick breather, was headfirst into training again, swimming about 90 kilometers (56 miles) per week, or 20–30 hours. She was in the water six days a week, doing longer swims on the weekends and pulling occasional doubles during the weekdays, all while working her full-time job as a recruiter for Encompass Health.

When she finally stood on Samphire Hoe Beach in the dark on September 15, she felt ready but nervous. And it wasn’t long before she felt worse.

There’s nothing glamorous about marathon swimming. Swimmers generally stroke through the water alone—in Thomas’ case with occasional company from one of her three swimming friends who were part of her support crew on the boat. If there’s noise, it’s dampened by the earplugs. When the sun was down, or when neither shore was in sight (which was most of the time), the boat was the one thing she had to look at.

The boat led the way, its captain serving as navigator for Thomas, keeping her on the best course. Both times she reached France, she touched the other side at Cap Gris-Nez, the nearest point on the east side of the Channel.

Sick for the first two laps across the English Channel, Thomas finally started to feel better (though tired) around hour 30. Photo by Jon Washer

Thomas paced each lap to try to align with the change of tides, which she says turn about every 12 hours. “You don’t necessarily want to go too fast because if you get there too soon, the tides won’t have turned,” she says. If you don’t hit the tides right, you end up swimming against them instead of with them.

Even with her pacing—11.5 hours on the first lap, then 12.5 hours, 13 hours—Thomas still had to sprint both times she reached the Cap, fighting against the currents to touch the rocks.

Thomas was sick for her first two laps, nauseated and throwing up everything her crew slung down to her in a water bottle connected to a rope. Halfway through the swim, she was ready to climb into the boat and leave the Channel behind. It was dark again, a day after she’d started.

“You’re going to be fine. Just swim until the sun comes up,” she remembers her crew telling her.

“So that’s what I did,” she says. “I swam until the sun came up and I started to feel better. Between hours 24 and 30, it was awful, and then we were OK after that.”

On her last turn at the rocks on the Cap, she scooped hot oatmeal out of a mug and got ready for the last stretch. It ended up being the longest lap of all: 17 hours, the last bit in a fight against currents pushing her backward. Her crew told her to sprint, “which is not what you want to hear at hour 53 of a swim,” she says, so she put her head down and swam as hard as she could.

When she finally crawled out of the water at Shakespeare Beach at 6:30 a.m. on September 17, her first time on dry land in more than two days, she was dazed and surprised by a crowd of strangers there to meet her with peanut M&Ms, one of the few things she was able to successfully eat in the water, and a glass of champagne which she tried to sip but immediately gagged at and couldn’t swallow.

A few hours later, back in the Airbnb she’d rented with her husband, Thomas took a bath and climbed into bed before waking to a storm of media requests. Now back in Colorado, Thomas doesn’t have her eyes on a new goal just yet. She plans to take the next year easy in terms of her own swimming, help a few friends with their goals, and go camping with her fly-fishing husband.

“When I first booked the English Channel, it was another conquest, another notch on my belt, and it didn’t really have a whole lot of meaning to me other than I thought it was cool,” she says. “But after going through cancer and literally not knowing if I was going to physically be able to do something like this again, I’m just proud of the fact that I was able to physically and mentally recover … and get to a place where I even had the confidence again to swim something like this.”