In this summer of heat domes and record-breaking global temperatures, finding a place to cool off is more important than ever. You can go to a movie or a museum—if you want to buy a ticket. You can head to an air-conditioned bar—if you don’t have kids who also need to escape the heat. Or you can just stay at home and blast your own air conditioner—a rather lonely prospect, if you ask me.

But there’s a better way to cool down, no air-conditioning or entrance fee required: America’s hundreds of thousands of public pools. Cool water, fresh air, exercise, babies, teenagers, seniors: They’re all at the pool. In a time of increasing heat and social isolation, public pools are a blessing.

Where I live, in Manhattan, we have several outdoor pools smack in the middle of the sultry cement jungle. For that, my neighbors and I can thank, among others, Robert Moses, the urban planner who was instrumental in creating New York City’s public pools. Moses was a staunch advocate for public swimming. “It is no exaggeration to say that the health, happiness, efficiency, and orderliness of a large number of the city’s residents, especially in the summer months, are tremendously affected by the presence or absence of adequate bathing facilities,” he wrote in 1934.

Swimming does, in fact, have important benefits for physical and mental health. Perhaps most crucial this summer: Immersing yourself in cold water can quickly lower your body temperature on a hot day. Swimming is fantastic aerobic exercise, and it’s easier on the joints than many other activities that raise your heart rate. Aerobic activity reduces stress, and swimming in particular has been shown to improve mood. In one preliminary study, swimming in the cold ocean reduced feelings of depression up to 10 times as much as watching from the beach did. In a separate case study, a woman with treatment-resistant depression experienced a significant improvement in her symptoms after swimming in open water once a week.

I’ve loved swimming since I was a young child, when my father taught me, and even now, whenever I’m in a bad mood, I reflexively take myself to the water. I’ve always thought the mood-boosting effects of swimming were solely the product of the exercise and the resulting flood of endorphins in my brain—that I might get the same effect from, say, a hard weight-lifting session or a long run. But the thing is, the studies that find that swimming lifts your mood tend to involve swimming with other people. Perhaps the social contact is part of the magic too.

[Read: Who should public swimming pools serve?]

Early in the pandemic, when life ground to a halt, the indoor pool where I swim in the offseason had very strict rules. You had to reserve a time, and there were never more than two people in a lane. It should have been a swimmer’s dream: no crowd and a guaranteed lane. I swam just as hard and for just as long as usual. But to my surprise, the experience was devoid of pleasure.

I didn’t understand why until one hot evening this summer, when I returned to Hamilton Fish, my favorite public pool in New York. It’s a sprawling, irresistible pool, flanked by trees, beautiful early-20th-century pavilions, and a plaza where people lounge about. When pools reopened during the first year of the pandemic, the city initially suspended adult hours at its outdoor pools in favor of free—and riotous—swim. When I visited, kids were shrieking with glee, horsing around and splashing everyone in sight. A handful of serious swimmers were trying in vain to find a lane for a workout, but I mainly paddled around with the kids, enjoying the cool water.

After I did manage to find a lane to do laps, a group of kids approached me and asked if I would teach them how to do a flip turn. We had a blast practicing somersaults in the water. At closing time, after the lifeguards drove the reluctant throng out of the pool, I stood under the cold outdoor shower with the other swimmers, struck by the strange intimacy of it all: Here we were, complete strangers, a diverse collection of humanity, practically naked and standing around having fun together. Everyone got along.

That is the whole, beautiful point of a public pool: to exercise and cool off with loads of people around. In the Southwest, where temperatures have been climbing above 100 for weeks, these facilities are a lifeline. Everywhere else, they can make the difference between a lonely, uncomfortable summer day and a joyful one. And yet, thanks to budget cuts and lifeguard shortages, fewer and fewer Americans have easy access to a municipal pool these days.

[Read: How lifeguards lost their luster]

Back in 1934, when Moses extolled the virtues of public pools, the United States was in a pool-building frenzy. Many of those pools were racially segregated, so not everyone could swim together, but in time they came to be melting pots, even as cities invested less in their upkeep and many white residents flocked to private facilities.

Now, as the heat builds in American cities, Moses’s ideas about the role of community swimming in public health and happiness are more relevant than ever. If you can get to a public pool this summer—even if you could also use a backyard pool—make sure you take the plunge. Sure, it will still be blazing hot outside when you’re done, but the refreshment and relaxation will linger long after you’ve dried off.

Over the past month, record-setting high temperatures have been recorded in several places across the northern hemisphere. Dangerous heat waves in Europe, Asia, and North America have driven people to nearby beaches, lakes, and water parks to find relief. Collected below, recent images show people and animals doing what they can to beat the heat.