Because my father has forever declared that I was “born an adult,” it did not surprise me that a guru I met told me I needed to nurture “child Mattie.”

When I asked her how, she shut her eyelids and “meditated on it.” She was still for three minutes, which is a long while to watch a person try to cure you. Looking at me, she wanted to know how often I swam.

“I splash around,” I answered, but I admitted that I had not swum a full lap since summer camp. She prescribed lessons. She said it would be good for me—restorative and important.

I do not trust shamans. I do not chant. A sample sale produced the most transcendent experience I have ever had. But I liked the guru, and I have always liked to swim. For at least seven summers, I took weekly lessons. I read Swimming Studies and loved it.

So I heeded the guru. I spent $25 on a black Nike one-piece and enrolled in an intermediate clinic for adults at the JCC Manhattan.

Within minutes, I was breathless.

“Every lap should make you feel like you’ve run a mile,” the instructor commanded. “You want to move—a lot.”

For 60 minutes that passed in what should be seconds, I do. I practice kicks and strokes. I learn to time breaths to move faster. I swallow a lot of water. As I did when I was very little, I trace the outline of my frame with my fingertips. It seems so alien and pale under the water that I have to marvel at all of it—it is so good.

Swimming is not the “new hot workout.” It will never be The Bar Method. I was glad for this. Every time I swapped street clothes for a swimsuit, I reveled in the dowdiness of it all. No matter how perfect she looks in spandex, even Karlie Kloss cannot elevate goggles and silicone bathing caps. They resist fashion. These goods are too practical to be chic. Be happy: It alleviates the pressure. When I pulled mine on, they gave me permission to be less impressive. There are very few chances to showboat in a swim class for grown-ups. Kickboards are just not for It girls.

But for all the freedom and child-like wonderment that these hours underwater promised me, they created new forms of unease.

Pool water is a ruthless, chemical marinade. Whenever I remembered that dozens of snot-faced children had splashed in it that morning, I was cheered to swim in a vat of Purell. That solution is inexact, though, as it zaps bacteria and microbes and moisture, too.

To save blond streaks, I got wet before I dunked in the pool. Rumor has it that hair is a total drunk—it soaks up whatever substance it touches. I wanted it to be too wasted for chlorine.

At the end of each session, I had to slather lotion all over. Once, I did not remember to take such precautions. The next morning, I found dozens of shreds of skin on my sheets. They looked like coconut flakes. Because I do not have açai-bowl ambitions, I invested in Bottega Organica Swimmer’s Body Oil. Aptly named, it smelled like Olympic victory and boasts vitamins from carrots, orange peel, and grape leaves. I slicked it on both pre- and post-swim. I resisted the temptation to use it in a vinaigrette.

And yet for all my preventative measures, chlorine would not be underestimated. The L’Oréal Kids Tangle Tamer that I so craved when I was 10 would have been no match for it. It outstripped the most extravagant conditioner I have ever known. Three lessons in, my legs were stronger, my abs were tighter, and my hair was straw. To combat what it wreaked, I alternated David Mallett's Mask No. 1 L'Hydratation and Kiehl’s Olive Fruit Oil Deeply Repairative Hair Pak. They turned each strand into spun gold. No—really. I tried Christophe Robin's Cleansing Purifying Scrub With Sea Salt, for which I scoured each square inch of my scalp like it was an HGTV renovation project. When it was over, I understood Ty Pennington better and had more refined follicles.

Venturing into the great and humid outdoors, I devised looks for wet hair that did not necessitate power tools. While I the GHD Air Hairdryer is more beloved to me than most humans, I preferred to leave it at home. For now, I have weak arms. Talk to me when I have mastered the backstroke. To the pool, I instead lugged Bumble and bumble's Don’t Blow It—a so-called “(H)Air Styler' that is supposed to enhance natural textures. It made mine wavy and more attractive in its messiness, which thrilled me. A generous spray of Shu Uemura's Wonder Worker helped on particularly humid days.

And while I was reluctant to turn heavy moisturizers into a form of modern embalmment, I started to double down on Jurlique's Nutri-Define Superior Retexturising Facial Serum—a long name for a product I like that saves skin from the outside world.

It is almost too awful to realize that summer will be over soon, and these lessons in “how to be in water' will end. The fact is that no workout or treatment for existential and reckless abandonment is so wonderful that it excuses wet hair in the winter. Pneumonia is even less chic than swim caps.

—Mattie Kahn

Photos courtesy of the author.

Post-swim, protect your hair from the sun with hair SPF. [ead more from Water Week here.