In his letters, Seneca writes that he started every year by taking a cold swim. He described himself as the “cold-water enthusiast.” And “just as naturally as I would set out to do some reading or writing, or to compose a speech,” he said he loved to take “a plunge into the Virgo aqueduct [present day Trevi Fountain].” He couldn’t have known any of the since proven health benefits. He wasn’t competing or on a swim team. He wasn’t going down to the canal to clean or freshen up. So why was Seneca so drawn to the water? In her latest book, Why We Swim, bestselling author Bonnie Tsui uncovers why humans, despite not being natural-born swimmers and despite the dangers, can’t escape an innate affinity for the water. In our interview below, Bonnie details some of those health benefits Seneca didn’t know he was enjoying, why the water forces one to be present, and how swimming has helped her confront and embrace mortality. Please enjoy this interview with Bonnie Tsui!

We know you’re a voracious reader. Have you read much of the Stoics? Do you have a favorite? Any quotes or exercises that have especially resonated with you? 

I haven’t read a ton of Stoic philosophy, but a lot of it lives in my approach to life. I like the elemental way that Seneca sets up the understanding that we are in control of some things and not others: “Floods will rob us of one thing, fire of another. These are conditions of our existence which we cannot change. What we can do is adopt a noble spirit, such a spirit as befits a good person, so that we may bear up bravely under all that fortune sends us and bring our wills into tune with nature’s.” The sooner we are copacetic with that, the better we can find ways to work with the world, not against it. It’s a pretty essential way to understand swimming, too: that we learn to work with water, not against it, to get better at conducting ourselves in it.

You set out to find an answer to the question that titles your new book Why We Swim. Even as a lifelong swimmer and water enthusiast, what were some of your favorite new discoveries about the deeper instincts driving humans to the water?

I loved learning about how we are biologically driven to respond to certain set points in the environment—that our brains love to be near water and blue spaces. That we love immersion and the feeling of physically being in water, but that our brains also produce more alpha waves—those wavelengths associated with relaxation, calm, and creativity—when we are merely listening to or looking at it. That the science is just starting to catch up to explain what we knew even the time of the Stoics: There is a benefit to both body and mind to get in and swim.

Seneca called himself a “cold water enthusiast” and liked to celebrate the New Year with a cold plunge. You talk about some of the health and general well-being benefits of cold water throughout the book. Could you share some of those with our readers? And do you find there is a philosophical component too?

The studies show clear therapeutic benefits: cold-water immersion significantly boosts metabolic rate and dopamine levels and reduces tension, fatigue, and pain. It also boosts circulation and vascular function over time. I do think there is a philosophical resonance—that if you push past initial discomfort and fear, you can get to a place of acute awareness and experience. That you dance near death to feel more alive.

One way the Stoics sought to cultivate wisdom was to bathe in beauty, to marvel at the wonders of nature, to find beauty in everyday life. That seems to be one of the key messages you impart in your book. Why is that such a powerful practice to cultivate? Any tips for how people can make it a practice in their daily lives?

Swimming is my way of being present in the world. When I get into the pool or the ocean, the world falls away in a roar and a hush, and I am attuned to the immediacy of the water. What it feels like, looks like, tastes like. How it feels on my skin, what the light looks like slicing in. Are there animals around, or wind, or swell? What flavor of blue is it today? You can’t come away from the water and not feel transformed, or without a slightly altered perspective on what you will confront next in the day. I have a busy brain that is often preoccupied with what came before or what comes after, and in the water I am forced to take stock of now. That’s really valuable.

The one thing that appears the most in Marcus Aurelius, Seneca, and Epictetus is the importance of confronting our mortality and how most of us either deny our mortality or are incredibly anxious about it. We learn in your book how swimming has helped you with those things. Can you elaborate for our readers?

The practice of swimming for me is also a practice of confronting mortality every time I go out into open water. The pool is a safe, circumscribed space that doesn’t change, so the way I swim in it is with more of a wandering mind. The ocean is different: it commands your attention, and there is never a time when I get in that I don’t remember it can kill me. That is a strange thing to contend with, and to recognize and accept. It helps me to look at mortality in the eye and make the conscious decision that moving in a place of risk is worth doing. It colors the way I view the rest of my life—that it will inevitably end in death, the way all of our lives do, but that I don’t have to give up pleasure and joy and wonder in the process of recognizing that truth.

Lastly, any book recommendations?

I love Crissy Van Meter’s novel Creatures—it’s a story about a woman who lives on a small island. Her life is inextricably intertwined with the sea—her intimacy with the sea underscores her confrontation with a lot of other hard realities, and yet she is still able to love and embrace the difficult people in her life throughout the book. I love Ted Chiang’s work, especially his short story collection Exhalation, which grapples with philosophical realities of a different sort, in the near future, but still explores questions of control. Somehow both of these authors are simpatico in my mind.