In general, samurais score very highly on the pop culture favorability charts. However, there is a most impressive but relatively underappreciated way of the samurai. It's called Nihon eiho — a type of classical Japanese swimming that dates back to feudal times and evolved because, as Japan is a nation of islands, it greatly behooved samurai warriors to master the water in deadly and efficient fashion.

There are many schools — or ryu — of samurai swimming, and they range from marathon floating techniques to "silent swimming" wherein the warrior moves imperceptibly through the water, heads and arms above the surface, dry weapons at the ready.

So far as it's possible to determine, Bonnie Tsui did not answer questions in a recent interview whilst using any of the Ways of the Ryu to bisect her way through the chilly waters and cruel currents of San Francisco Bay.

But she probably could have.

Tsui is the author of the book "Why We Swim," a compulsively readable narrative comprised of a rich array of anecdotal bits — from Lord Byron to, yes, samurai swimming, and from history and science to memoir andcial science — all filtered through the prism of swimming. Tsui is also the May guest for our "Read of The Day" book club in partnership with Bank Square Books, and she'll take part in a virtual discussion of "Why We Swim" Thursday.

Yes, Tsui is a committed swimming enthusiast. Her mother and father met at a swimming pool in Hong Kong, and she was born and raised in New York, swimming at beaches as a child and for her high school team. Now a wife and mother of two in San Francisco, Tsui is still a very active swimmer who firmly believes not just in the physical conditioning benefits of swimming but also the mental therapies and even an almost spiritual connection between humans and water.

But "Why We Swim" is not a how-to guide, and Tsui is not an athlete whose goal is to exhort the reader to get off the couch and start swimming laps. Rather, the book is a sort of fan's crush-note to swimming — and in this case the fan is brilliant and curious and has a prose style like the most seductive of nature writers or thriller authors.

It might be said Tsui writes with the smooth and lulling rhythm of, well, a natural swimmer.

"I never gave much thought to how swimming informed my writing." Tsui is on the phone from her home in San Francisco. "I just thought swimming was something I love to do, and it got me settled before a day of writing or going about life in the world."

In addition to "Why We Swim," Tsui is an award-winning journalist, a frequent contributor to the New York Times and California Sunday Magazine, and is the author of the "American Chinatown: A People's History of Five Neighborhoods."

"'Why We Swim' was the first project that gave me the opportunity to think about that connection between writing and swimming," she says. "Suddenly, I was thinking about getting out of the pool and going to the office to transcribe what was in my head while I was in the water. I wanted to write not just about the sensory experience of swimming but also how that affects what I do out of the water and with what life throws at me."

A marvelous and friendly conversationalist, Tsui is the sort of researcher who attacks a topic for the sheer joy of learning — and part of the fun is following all the tangents that continually open during the process. In researching the book, she talked not just to elite swimmers with intriguing backstories that illustrate the goals and rewards of swimming — often in elite or even daredevil fashion — she also spoke with numerous scientific experts.

A range of swimmers

That explains why readers of "Why We Swim" will meet Guðlaugur Friðþórsson, who as an Icelandic fisherman in 1984 survived a capsized boat and swam for six hours in 5 °C water before reaching shore. There's no biological way he should have been able to do that, but it turns out there is a scientific explanation. To find out what it was, Tsui traveled to Iceland and spent time with Friðþórsson, who is a national hero despite a humble and quiet demeanor Tsui conveys beautifully.

The reader will also meet Bajau swimmers from Indonesia, who over the course of generations have developed the ability to free-dive for 10 minutes in deep ocean water — because over that time their spleens have evolved and are now 50% larger than average. This expands the number of oxygen-rich red blood cells that can be released into the blood stream. 

Tsui spent time with Dana Torres, who became the oldest-ever Olympic swimmer. At 41, Torres swam the fastest 100-meter freestyle split in relay history as the anchor of the gold medal-winning 4x100 meter medley relay. Tsui also swam with Kim Chambers, who turned to the water after a land accident that led doctors to predict she'd never be able to walk without aid. Chambers is one of very few people to complete the Oceans Seven marathon open water and channel swim challenges including the Strait of Gibraltar, the English Channel, and the 27-mile Moloka'i Channel.

The Samurai Way

Tsui also visited Japan to learn about the discipline and philosophy of the swimming samurai. She watched sessions and spoke with swimmers and instructors.

"I was so surprised by the wonderfully ordinary mix of people who practice this," Tsui says. "It was amazing to see how, in real life, it's a thing they just do and spend much of their lives perfecting because it helps them face the stress and rhythms of modern life.

Tsui even went to a pub with Midori Ishibiki, one of the truly elite female instructors, and says, "It was neat to talk to this young woman about this very old tradition that keeps her afloat in modern times. It's taken her a number of years to reach this level and it was touching to hear her talk about the efficiency, beauty and elegance of working with the water, and how it s so contrary to the pace and anxiety of technology and the way we live."

Swimming to freedom

Back home in San Francisco, Tsui remains an active swimmer. She's on a swim team and participates regularly in frigid outings in the bay. She's even successfully made the swim across San Francisco Bay to Alcatraz. It's pointed out to her — certainly not for the first time — that the California Bureau of Prisons put the infamous penitentiary on Alcatraz for a reason.

"I hadn't really thought about it seriously," Tsui laughs. "But I did look out there at Alcatraz and think, 'I wonder what it would be like to do that?' And I knew people could do it and had been doing it. But there are so many beautiful, inviting bodies of water that are challenges — and San Francisco Bay is NOT that. It's really cold. There are dangerous currents and sharp rocks and shipping traffic. So, naturally, the more I thought about it that context, the more I wanted to try it."

When a friend who'd done it approached her to give it a try, Tsui did — and, yes, it was frightening and hard, but the more she swam, the more it became an exhilarating experience.

"Now, every time I see Alcatraz, I have a different understanding of something I'd always seen in a certain way," Tsui says. "We all need these moments of euphoria and ecstasy, hopefully in low-risk situations or not pushing beyond your abilities. The open water allows you to get to the edge of your ability and then back off. You're dealing with fear and anxiety all the time you're in the water." She laughs again. "I think that's beautiful."

To see and hear

Who: Author Bonnie Tsui

What: Discusses her book "Why We Swim" with The Day's Rick Koster as part of our "Read of The Day" book club in partnership with Bank Square Books

When: 6 p.m. Thursday

How much: Free, but registration required: https://www.banksquarebooks.com/event/virtual-read-day-bonnie-tsui-why-we-swim

For more information: (860) 536-3795