Update: The Mighty Mermaids attempted their swim on July 22! Find out how they did here.

How hard is it to swim the English Channel? Consider this: 807 people summited Mount Everest last year, but only 1,832 people have swum the English Channel successfully since 1875. Come July 22nd, a six-woman relay team composed of top U.S. Masters long-distance swimmers will give it their best shot. Collectively, they’re known as the Mighty Mermaids.

The Mermaids are Christie Ciraulo and Veronica “Roni” Hibben from California, Jenny Cook of New York, Karen Einsidler of Florida, Tracy Grilli of New Hampshire, and Nancy Steadman Martin of New Jersey. For years, they knew each other only by reputation. And what reputations! Lifelong competitors, they are among the top long-distance swimmers for their age group in the world. All members of United States Masters Swimming (USMS), a special class of competitive swimmers aged 18 and older, they hold hundreds of individual world and national titles.

A Team Assembles

In 2005, Christie Ciraulo brought the group together as she was approaching her 50th birthday. “I wanted to swim for another 40 years, but it can be a very solitary sport,” Ciraulo recalled one overcast day on the beach in Santa Monica. “I thought, How can I make it not so solitary?”

Her solution: Form a relay team of “fast, fun and over 50” women who would commit to an annual open-water race. Only super-competitive types need apply.  Ultimately, Ciraulo, a former public-relations professional, corralled a diverse group of working women—travel agent, executive secretary, lawyer, life-insurance agent, and wireless tech executive—who threw their swim caps into the pool.  It took another three years for the group to all turn 50 (that way, they stood the best chance to win their age group of 50-59), get organized, and brainstorm which races they would enter. By 2008, they had chosen to swim across Lake Tahoe and have never looked back.

After that, the Mermaids took Manhattan—swimming 28.5 miles around the island. The next year, they swam from Catalina Island to the Southern California mainland. And so it went. Across Tampa Bay. The entire length of New Hampshire’s Lake Winnipesaukee. Down the Mighty Red River of the North, a 38-mile race from Minnesota to North Dakota.

Read More: How I Got In the Best Shape of My Life After 50

Choosing the Channel

The English Channel will be their 12th relay together. It is considered the ultimate long-distance open water challenge—21 miles in choppy water in which swimmers can expect to encounter jellyfish, masses of seaweed, and random piles of planks bobbing by. Also gigantic tankers: 600 of them routinely ply this busy shipping lane along with hundreds of ferries and other vessels that cross daily. Each team member will swim the channel for an hour in rotation until they reach France. The average relay crossing time is 12 hours.

They’ll be ready—they always are. For the Mermaids, swimming isn’t just a pastime, it’s a way of life. They all swim about 10 hours a week for different USMS clubs near their homes, being coached and entering competitions individually as their schedules allow. Most swim four to seven days a week, following their own workout and coaching regimens in the pool and open water.

Synchronized Swimming

After 12 years, their group dynamic is a well-oiled machine. Mermaid business gets discussed every three weeks on conference calls, dubbed “Conch Calls.” Ciraulo sets the agenda with input from everyone (Relays to consider? Family responsibilities?) Steadman Martin often serves as COO, dispensing assignments for gear such as light sticks, lanolin, and Vaseline (and for the Channel—chemical hand warmers.)

Travel agent Jenny Cook weighs in on where to stay (sometimes the group tacks on a post-race road trip).  Everyone has a task, down to getting done up in the official nail polish color and getting the team suit (there’s a new design for each race). For the Channel, they have custom-made red-and-blue-striped white swimsuits and will warm up on the deck of their escort boat, the “Sea Satin,” in blue sweatpants and red sweater jackets adorned with an American flag patch.

Toughing It Out

The Mighty Mermaids from left, Roni Hibben, Jenny Cook, Karen Einsidler, Christie Ciraulo, Nancy Steadman Martin, Tracy Grilli.

The Mermaids have total confidence in each other—it’s weather conditions they worry about. Waves can start out flat, then get frothed up to six feet without warning. The water might be a “comfortable” 60 degrees—or as frigid as 52. And wetsuits? Not permitted.

“We are all super-veterans in open water. We’ve all done two-hour swims in 61 degrees or below many times,” Christie Ciraulo said. “But right now [the Channel] is sitting at 57—and that’s going to be hard.” They risk developing hypothermia, a medical emergency that occurs when your body loses heat faster than it can produce it.

But these superb athletes don’t dwell on “what ifs.” Two Mermaids have already swum the Channel solo. Nancy Steadman Martin is the current solo record-holder for her age group at 11 hours and 20 minutes. Karen Einsidler swam it at 58 degrees. They are clear-eyed about what’s ahead. “It’s a tough swim because you see no progress—you’re too far out to see the shore,” said Einsidler. “And to be honest, the chop is a lot worse than anything we have seen before.” Other Mermaids are grateful they get to swim the Channel at all. “For me, this is an opportunity I would never have had without the team,” said Jenny Cook. “There is strength in our numbers.”

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An On-Shore Sisterhood

The Mermaids have faith in the kinship built up over more than a decade—and it’s a strength that doesn’t end at the shoreline. They have helped each other come back from

injuries and losses to emerge stronger than ever. In the wake of Einsidler’s bout with breast cancer, the Mermaids relayed to raise funds for research. When Cook had shoulder surgery, she recuperated at Roni Hibben’s home. “It changes form, but it’s much like water: we ebb and flow among each other but our support is always there,” she recalled.

Or as Nancy Steadman Martin put it so succinctly, “They say blood is thicker than water, but for us, water has been pretty thick.”

The Mighty Mermaids will swim across the English Channel starting on July 22nd. We’ll update you on the results.

Photos by David Grilli.