Denis Crean, a businessman and longtime swimming coach, has pursued his passion for open-water swimming in just about every kind of waterway. He has overcome headwinds at Lake George in Upstate New York, traversed the Tampa Bay and negotiated tricky conditions during a 28-mile marathon swim around Manhattan. “I remember watching the Empire State Building go by and thinking, ‘Wow, we are going fast with the current,’” he said.

But Crean said his first love — the one that taught him important life lessons — is the ocean.

“When things are stormy and waves get big, how do you roll with it?” said Crean, who has also swum across the English Channel and Southern California’s Catalina Channel — his toughest challenge. Navigating changing currents has taught him that “things will work out, that you will get to the other side, if you observe, adapt and change.”

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With summer approaching, many are dreaming about stretching out on the beach with a good book or taking a quick dip in the surf. But for Crean, the 64-year-old founder of WaveOne Open Water swim club in Washington, a vigorous workout in the ocean is the main attraction. And he has plenty of company.

Ocean swimmers say their ranks are growing as people realize the unique boost — particularly for mental health — provided by a sturdy stint in saltwater. The activity, aficionados say, appeals to people of different generations and fitness levels, from triathletes to retirees.

While any kind of swimming provides excellent exercise, swimming in the ocean and other natural bodies of water provides a connection to nature that seems especially effective at reducing stress. “It’s like forest bathing,” the Japanese practice of immersing oneself in nature, said Irina Todorov, a family medicine physician at Mayo Clinic in Jacksonville, Florida. “It’s relaxing and meditative.”

‘Spiritual cradling’

Marilyn Spitz, 75, who lives in Puerto Rico and Lewes, Delaware, said her almost-daily swims feel like a “spiritual cradling.” Since starting regular ocean swimming two years ago, she said, her resting heart rate has slowed, and her blood pressure has declined.

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The activity provides other benefits as well, including a much-needed jolt of adventure and chance to make friends. “I’ve swum at this one location thousands and thousands of times, and it’s different every single time,” said Katie Godec, the athletic director of triathlon group LA Tri Club, who frequently swims near Santa Monica, California.

The salt in the water is helpful, too, providing a buoyancy that makes it easier to float and acts as a natural exfoliant, “leaving you with smoother and softer skin,” said Elizabeth Jones, a professor of dermatology at Thomas Jefferson University Hospital in Philadelphia.

But there are downsides to ocean swimming as well. The risk of drowning is higher in open water than in a pool, experts say. And many of the ocean’s hazards — including rip currents, wildlife and pollution — are challenging for even the most experienced swimmers.

“You need to respect the water,” said Lori A. Sherlock, an exercise physiology professor at West Virginia University’s School of Medicine. During a 4.4-mile swim across the Chesapeake Bay, Sherlock, who has participated in several triathlons, said she encountered a jellyfish “every fifth stroke” and hit currents so strong she was almost “pulled into one of the pylons, which was covered with sharp and pointy barnacles.”

The need for stamina

Newcomers to ocean swimming don‘t have to be triathletes, veterans say. But they do need to be cautious — and proficient at basic strokes and skills such as treading water. Crean said aspiring ocean swimmers should be able to swim 500 meters — the equivalent of 10 laps in an Olympic-size 50-meter pool — without stopping. “You need to have the physical stamina and wherewithal to negotiate through water,” he said. His group conducts clinics and races in the Potomac River, the Atlantic Ocean and elsewhere.

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Once swimmers decide to try ocean swimming, they should be accompanied by an experienced companion — never go out alone — and alert any lifeguards on duty to their plans. They should wear brightly colored caps and drag tow floats attached by leashes to waist belts to make sure they can be seen by other members of their group and passing boats.

When 50 or so people gather every weekend to swim at Florida’s Fernandina Beach, safety is the top priority. “We swim to a specific distance marker, a quarter mile or a half mile, stop and check on everyone, and then begin swimming again to the next distance marker,” says Matt Dunn, co-founder of Salty Sports Society of Fernandina Beach, which organizes open-water swimming events and competitions. The swimmers wear colored caps and tow floats.

Shark bites, while terrifying to contemplate, are extremely rare. In 2024, there were 47 unprovoked shark bites globally, well below the 10-year average of 70, according to the International Shark Attack File at the Florida Museum of Natural History. A little more than half were in the United States.

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In Southern California, swimmers also keep an eye out for stingrays, which sometimes hide on the ocean floor. Jason Tootell, a former competitive swimmer who lives in Solana Beach, California, said he does the “stingray shuffle” when he enters the water, dragging his feet to scare off nearby stingrays.

Pollution and bacteria

An increasingly common problem for open-water swimmers involves intense storms linked to climate change. Such rainfalls can overwhelm outdated sewer systems, allowing untreated sewage — and illness-causing pathogens — to slosh into waterways. At the 2024 Paris Olympics, some swimming events were postponed or canceled after tests showed high levels of bacteria in the Seine following heavy rain. Similar concerns dogged the 2016 Rio de Janeiro games.

In addition to bacteria, “you can get all kinds of pesticides in the water” from agricultural runoff, said Elaine K. Howley, a freelance writer who runs the annual 8-mile Boston Light Swim in Boston Harbor.

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Beach sand itself is hardly pristine. It can harbor various microorganisms, including the germs that cause gastroenteritis. In Los Angeles in April, officials lifted a water quality advisory for beaches affected by the January wildfires, saying they didn’t find unsafe levels of chemicals, but they cautioned about possible beach hazards such as metal and sharp wooden debris. Experts say beachgoers should wear footwear for protection and wash their hands after leaving the beach.

Devotees of ocean swimming acknowledge such downsides but remain undeterred. They say the thrill of natural surroundings trumps the controlled environment of pools.

“There’s an artificiality to being in a pool with all that chlorine,” said Chris Noonan-Sturm, who lives in Lewes and founded Open Water Swimmers of Southern Delaware, a Facebook group that has more than 350 members. Like other open-water swimmers, she likes to try appealing spots in other locales.

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For some celebrated routes, swimmers have long waits. Susanne Blair, 65, of Sandpoint, Idaho, who swam across the English Channel, now wants to swim across the Strait of Gibraltar, but there is a two-year wait for a slot. “I’m not even on the wait list,” she said. The number of swimmers is controlled by the Strait of Gibraltar Swimming Association.

For Spitz, who swam around some of the Galápagos Islands this year, once was not enough. “We would jump in and swim among sea lions and all kinds of fish and the ocean felt so wonderful,” she said.