A Deep Dive into Core Strength and Breathwork: Swimming with a Weighted Mono-Fin Tail

The smell hit me first. That distinct, stinging perfume of municipal chlorine mixed with the rubbery funk of neoprene warming in the sun. I was sitting on the damp tile of a rec center pool deck, trying to shove my size-ten feet into what looked like a glittery straightjacket.

It was a Tuesday. I could have been doing taxes. I could have been drinking a tepid lager at a dive bar. Instead, I was greasing my ankles with conditioner, sweating profusely, preparing to become a mythical creature.

Welcome to the weird, wet world of mermaiding classes.

You might laugh. Go ahead. I did. When I first heard about the rise of mermaid swimming lessons for adults, I pictured a bachelorette party gone wrong. I imagined plastic tiaras and lazy drifting in the shallow end while sipping margaritas from sippy cups. I expected Disney.

I got Navy SEAL training in drag.

This isn’t just dress-up. It’s a subculture that has exploded from the niche corners of cosplay into mainstream aquatic fitness. And if you think it’s easy, I dare you to bind your legs together, strap a ten-pound piece of plastic to your feet, and try to swim fifty meters underwater on a single breath without passing out.

The shackle, I mean, the tail

Let’s talk about the gear. The fantasy starts with the aesthetic—scales that shimmer like an oil slick, vibrant purples and electric greens—but the reality is the mono-fin.

Hidden inside the fabric skin of the tail is a rigid, heavy fin that locks your feet into a fixed position. It’s a commitment. Once you’re in, you’re in. You can’t walk. You can’t stand. You are effectively paralyzed on land. You have to scoot your butt to the water’s edge like a dog with an itch. It’s humbling.

The instructor, a woman named Maureen who possessed the lung capacity of a sperm whale and the patience of a saint, stood over me.

“Don’t bend your knees,” she barked. “The power comes from the hips. If you bend your knees, you’re just a drowning bicycle.”

She wasn’t wrong. The mono-fin workout mechanics are unforgiving. In standard swimming, you can get away with sloppy kicking. You can flutter, you can flail. Here, physics is a cruel mistress. The surface area of the fin is massive. If you try to kick from your calves, the water pushes back with equal force. You go nowhere. You just burn oxygen and look ridiculous.

To move, you have to undo decades of bipedal muscle memory. You have to undulate.

The Core of the Matter

This is where the pain starts. And I mean deep, searing, muscular failure.

Mermaiding is marketed as whimsical, but it is, at its heart, a brutal core strength exercise. The movement—the dolphin kick—requires a fluid wave of motion that starts at your sternum and snaps through to your toes. You contract your abs to pull your hips up, then fire your glutes and lower back muscles to drive them down.

Repeat this. Again. And again. Now do it while holding your breath.

After ten minutes, my abs felt like they were being shredded by a cheese grater. We’re talking about the kind of functional core training that makes Pilates look like a nap. You use the entire anterior and posterior chain. Every inch of your torso is engaged to propel that heavy fin through the water’s resistance.

Maureen swam past me, a blur of turquoise. She moved with a terrifying silence. No splashing. No wasted energy. Just a smooth, sine-wave motion that propelled her half the length of the pool in three seconds. She looked like a predator.

I looked like a dying worm.

“Belly button to spine!” she shouted from the surface. “Roll through the water! Stop fighting it!”

I was fighting it. I was fighting the water, the tail, and my own poor life choices. But then, a moment of accidental competence. I tightened my stomach, pressed my chest down, and let the wave travel.

Whoosh.

I shot forward. The drag vanished. For a split second, I understood the appeal. The speed you can generate with a weighted mono-fin is addictive. You feel superhuman. You feel sleek. Then you hit the wall and realize you can’t use your legs to turn around, and the awkward flailing returns.

Don’t Breathe

If the physical exertion is the hammer, the breathwork is the anvil.

You cannot gasp for air when you are pretending to be a fish. It ruins the illusion. More importantly, you spend most of your time underwater. This brings us to the most surprising aspect of the class: it’s basically an intro to freediving.

We spent the first twenty minutes of the session on dry land, lying on yoga mats, learning how to hold your breath longer. Maureen walked us through diaphragmatic breathing, C02 tables, and the relaxation response.

“Panic is the enemy,” she told us. Her voice was level, almost hypnotic. “When you feel the urge to breathe, that’s just carbon dioxide building up. You have oxygen left. You have time. Relax.”

Easy for her to say. She wasn’t the one encased in spandex.

But the breathwork techniques used in mermaiding are legitimate. They borrow heavily from yoga and competitive freediving. You learn to lower your heart rate. You learn to ignore the screaming alarm bells in your lizard brain that say, Surface! Now!

This mental game is what separates mermaid swimming from a standard water aerobics class. You are constantly managing your internal state. If you tense up, you burn oxygen faster. If you get scared, you burn oxygen faster. To survive the lap, you have to find a state of Zen calm while your muscles are working at maximum output.

It’s a paradox. High exertion, total relaxation.

I tried to channel my inner dolphin. I took a sip of air, ducked under, and pushed off. One undulation. Two. The silence of the pool wrapped around me. I watched the tile line pass. My lungs started to burn around the halfway mark.

Panic.

My brain said, Kick harder.

Maureen’s voice in my head said, Relax.

I slowed down. I smoothed out the kick. The burning didn’t stop, but it became manageable. A background noise. I touched the far wall and surfaced, gasping not with elegance, but with life.

“Thirty meters,” Maureen said, checking her stopwatch. She looked unimpressed. “Not bad for a land-walker.”

The Tribe of Scales

So, who actually does this? Who pays good money to bind their legs and nearly drown on a Tuesday afternoon?

Looking around the locker room later (struggling to peel the wet tail off my legs, which is a slapstick comedy routine in itself), I didn’t see the stereotypes I expected.

There was a tax attorney. A grandmother of three who had just recovered from hip surgery. A burly guy with a beard who worked in construction and wanted to improve his dolphin kick for scuba diving.

The rise of adult mermaid classes isn’t driven by a single demographic. It’s driven by a collective desire to escape the mundane. The gym is boring. The treadmill is a hamster wheel of despair. But the water? The water is another world.

“It’s the only time my back doesn’t hurt,” the grandmother told me, wringing out her hair. “And frankly, it’s the only time I feel graceful. On land, I waddle. In the water, with the tail? I fly.”

There is a psychological release in the costume. You put on the tail, and you have permission to be playful. You shed the grey skin of your corporate identity. You aren’t a mid-level manager anymore. You are a shimmering, aquatic badass.

The mermaiding community is fiercely supportive. They trade tips on silicone lubricants (essential for getting into the tails) and argue about the best monofin stiffness for speed versus agility. They discuss PADI mermaid certifications with the seriousness of someone discussing a master’s degree.

Yes, that exists. You can get certified. There are levels. It’s a bureaucracy of fantasy.

The Danger in the Glitter

We have to talk about the risk. Because nothing this fun comes without a warning label.

Mermaiding looks silly, but it can be dangerous. The binding of the legs is a significant hazard. If you panic, you can’t tread water. You can’t frog kick. You sink.

“Shallow water blackout is real,” Maureen had warned us at the start. “Never swim alone. Never push your limits without a buddy.”

The industry is trying to self-regulate, pushing for safety standards in mermaid schools. Cheap, knock-off tails from the internet are the enemy—they can break, trap your feet, or drag you down. The good stuff—the professional grade silicone and neoprene—is designed with quick-release mechanisms. You can kick them off if you have to.

But the real danger is hubris. It’s thinking that because you look like a Disney character, nothing bad can happen. The ocean (or the deep end of the YMCA pool) doesn’t care about your sequins.

The Aftermath

By the end of the hour, I was wrecked. My abs hurt when I laughed. My glutes were trembling. My sinuses were full of chlorinated water.

I dragged myself out of the pool, leaving a trail of water and dignity behind me. I sat on the bench, shivering, wrapping a towel around my shoulders.

I watched the next group coming in. Advanced students. They slipped into their tails with practiced ease. They didn’t struggle. They slid into the water like seals returning home.

I watched them swim. It was mesmerizing. They moved in a synchronized pod, rolling and diving, blowing bubble rings that caught the light. For a second, the rec center dissolved. The peeling paint on the walls disappeared. There was only the blue, the silence, and the fluid motion of bodies perfectly adapted to their environment.

It wasn’t silly. It was beautiful.

I walked out into the parking lot, back to the grey reality of pavement and traffic. My gym bag felt heavier, weighed down by the wet, scale-printed fabric.

I realized I was standing a little taller. My core was still engaged, a phantom sensation from the hour of struggle. I took a deep breath—diaphragmatic, filling the belly first—and unlocked my car.

Is mermaiding going to replace CrossFit? Probably not. You can’t do it in your garage. But as a way to trick yourself into the hardest abdominal workout of your life while pretending to be a mythical beast? It works.

I checked my calendar. I was free next Tuesday.

Maybe I’d buy my own tail. Something in black. Shark colors.

Why the hell not? The water is waiting.

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– Best, Stable Grace Staff Writers & Editors