The author’s instructor, Cookie DeJesus, at Marcus Garvey pool in Manhattan. (Ralph DeJesus/Ralph DeJesus)

On a hot weekday morning in late July, I arrived at Marcus Garvey Pool in Manhattan for a long-awaited meetup with a mermaid. Cookie DeJesus, also known as the Harlem Mermaid , has become a fixture in those chlorinated waters over the past several years, ever since she took a certification course at World of Swimming, a mermaid school in Brooklyn, and fell in love. Most days, she and her husband, Ralph, who designs many of her aquatic costumes, walk from their apartment to the pool so DeJesus, 57, can do laps in full mer-regalia as part of her workout. Today, as my instructor, she also brought a tail for me. 

Though I love swimming and have spent plenty of time paddling around public pools in New York, this was my first mermaid-related activity since I was a kid dressing up for Halloween. But other adults have thoroughly adopted the identity: Wearing a mermaid tail, in the water or out, has caught on in recent years , for reasons that include Disney fanaticism and the fact that the ensembles are Instagram candy. A search for #mermaiding on the platform surfaces more than 130,000 posts , and a cursory scroll through the results reveals merpeople perched poolside and on beaches and, yes, swimming with tails. There are mermaids who guest-star at birthday parties, perform in aquatic centers, engage in cosplay and photo ops — but also some who swear by tail swimming as a fitness routine. But is it actually a workout? That’s a question I sought to answer by trying it. 


Cookie with her husband, Ralph, who also makes her tails. (Mandi Renee/Ralph DeJesus)

At the pool, DeJesus met me outside, her crop of short reddish hair and bright green shorts reminiscent of a certain under-the-sea heroine. She carried about 30 pounds of tails and fins in a bag on her shoulder — a little bit of weight training that’s just part of the lifestyle. Not every pool allows mermaiding accoutrements inside, but DeJesus is a fixture at Marcus Garvey, where the staff welcomes her: She knows people, including the pool manager, whose daughter mermaids, too. 

When we sit down on the deck to slip into our outfits, the kids flock to “Mermaid Cookie”; she’s a natural entertainer who also appears at parties and events. First Cookie helps me strap the monofin — like a flipper for both of your feet — around my ankles. Then she demonstrates how to pull on my borrowed tail, which is made from Spandex swimsuit material (a basic tail can be found online for about $35; monofins start at about $25). DeJesus’s tail, however, is special: a neoprene number Ralph sewed himself and decorated with gold painted scales. “This is my mer-sister, Elizabeth,” DeJesus tells the handful of fans who have gathered around us, reminding them we’ll need some space. She believes it’s her responsibility to maintain the illusion, and in return they believe in her. Reverently, they back away to give us room. 

After showing me how to step out of my tail in case I start to panic — a real possibility, given how bizarre it feels to be in the water without being able to kick each leg separately — Mermaid Cookie explains her workout. Typically, it starts with jogging around the deck. But today we’re going straight to the core: Sitting on the edge of the pool, we bring our knees in line with the top of the water and practice slowly fluttering our tails before leaning back for reverse crunches. It’s tough on my lower abdominal muscles, and DeJesus reminds me to work from my belly, not my hip flexors, echoing a Pilates mantra. She normally does 20 reps and then swims, pausing to repeat the ab set at each corner of the pool. Long before we ever submerge, I’m already feeling the burn. 

Some mermaids have formalized their fitness routine through structured classes. Colleen “the Celtic Siren” McCartney, the co-founder of Metro Merfolk, which organizes meetups and mermaid classes, teaches an eight-session tail-swimming course in the Washington area. She always works out her students in the shallow end and emphasizes technique before anything else. “People want to kick their feet below the knees, but it’s not a hinging motion; it’s more like undulating in belly dancing,” she explains. “You need to point your toes and let it emanate from your core.” 


Participants pause underwater during a Metro Merfolk class in the District. (Colleen McCartney/Metro Merfolk)

Once merfolk-in-training have that down, McCartney puts them through circuits including Russian twists and “mermaid push-ups ” on the pool deck, barrel rolls through underwater hula hoops and, of course, plain old swimming. She recommends newbies begin with a smaller-size monofin, as bigger, heavier tails require more work. “Once you start doing it, you forget you’re working out,” she adds 

Standing in the four-foot end of the pool, Mermaid Cookie reiterates the point about the movement emanating from your abdomen, not your knees, demonstrating what she means with a splashy flourish of her tail. The kids erupt in happy screams. Then it’s my turn. I dive toward the bottom, propelling myself forward with a butterfly kick; seconds later, when I come for air, I’m already halfway across the pool. Immediately, I want to keep going. McCartney was right: This feels less like fitness than plain old fun. 


A collection of Cookie’s tails and fins. (Ralph DeJesus/Ralph DeJesus)

That’s not to say I wasn’t getting good exercise. Bianca Beldini , a doctor of physical therapy who is also a USA Triathlon Certified Level 1 Coach, often uses butterfly kick drills in her own training and with her clients. “Swimming is good for strength and flexibility, helps improve your cardiopulmonary functions, yet you’re not dealing with gravitational issues,” she says, adding that it can also be an excellent calorie burn. 

Though there is plenty of first-person anecdotal evidence about the fitness value of mermaiding, the practice seems too new to have prompted in-depth research. One study of professional mermaids does show a few potential health risks. Some are similar to the risks of swimming in general — ear infections, waterborne diseases, unwanted confrontations with sea life — while others are mermaiding-specific, including back pain related to wearing a fin and tail. Though I did in fact get water up my nose while I was swimming, that’s been happening all my life, and it has yet to deter me. 

For about an hour, Mermaid Cookie and I darted around the pool, chattering back and forth while swimming on our sides. When I ran out of breath, I laid on my back, languidly flipping my tail to stay afloat. Later, I attempted the full butterfly stroke, seeing how high my monofin could propel me into the air. From the deck, Ralph cupped his hands and yelled: “You’re a natural!” Mermaiding felt like a meld of dancing liberated from the particulars of technique and swimming removed from the rigidity of form. I spun and did a handstand for the first time in 20 years. It’s easy to understand why people become so enamored. 

Riding on the subway to Brooklyn later, feeling like I do after a hot yoga class — damp but wonderfully relaxed — it occurred to me that slipping on a tail felt a little like slipping back to a time before I was fussy about getting my hair wet or worried that the sun exposure was ruining my skin. Twirling through the water that morning felt joyful. Pretending to mermaid had the real effect of making me feel incredibly free.

Elizabeth Kiefer is a New York freelance writer who covers wellness issues.