Swimming is one of the best exercises for body and mind. It’s low impact, which makes it particularly great for beginners, injured athletes, or those looking for a good cross-training workout. And it burns almost as many calories as running, according to 2018 USDA physical fitness tables.

And yet, misconceptions and “alternative facts” about swimming abound. Many people, for instance, believe that you just can’t get a very good workout in the water. Others think it’s impossible to break a sweat in cool pool water. Then there are those who swear you have to wait an hour after eating to swim. But none of those things are true.

Here are the five most common swimming myths—and why they shouldn’t keep you from diving in this summer.

It’s true that water workouts are low impact, which makes them easy on your body if you’re nursing an injury or want to avoid joint or knee pain. But low impact doesn’t equal low quality. Swimming is one of the best whole-body exercises around, as it requires the use of pretty much all of the major muscles in your arms and legs, as well as your hips, glutes, back and abdominals, says Terry “Speed” Heggy, a level 3 certified US Masters swim coach.  

The reason you might not be getting a good workout? You could be holding your breath. “I see a lot of beginners go as far as they can without breathing, then come up for air, then put their heads down and again go as far as they can again without breathing,” says Heggy. “After about 200 yards, they are so fatigued that they have to quit.” Instead, you should be breathing every other stroke, or about as often as you would be during walking or running.

Recreational swimmers are just like the rest of the general population—some are trim while others are not. That observation has led many to conclude swimming isn’t a very effective way to lose weight. But if you take a look at elite swimmers, you’ll notice right away that they have very little body fat and a whole lot of muscle. Which means, the truth is much more nuanced.

Any activity that burns calories and helps your body create a calorie deficit can lead to weight loss. Swimming burns more calories than walking and almost as many as jogging. It’s true—a 154-pound person burns 255 calories for a half hour of slow pool strokes, versus 140 calories for the same amount of time spent walking and 295 for jogging. And you can torch even more by getting your heart rate up with swim intervals, says Heggy. He recommends starting with 10 times 100 yards, with 10 seconds of rest in between each one. “The important part is the 10 seconds of rest,” Heggy says. “You need to keep your heart rate up enough to get in an aerobic zone, where you’re breathing hard at the end of each 100 and leaving before you’re fully recovered.”

When you ramp up the intensity of any workout—in the pool or elsewhere—you’re raising your body temperature and your body responds by sweating. You just don’t notice it in the pool, since the sweat is immediately washed away, says Heggy. Just as you would during any other workout, you need to stay hydrated: Drink water if your swim workout is less than an hour and down an electrolyte-enhanced sports drink if it’s over an hour.

Also, it’s possible to overheat in the pool, especially if the water temperature is slightly elevated, which can be the case in outdoor pools. Olympic and FINA rules state that competitive swimming pools should be between 77 and 82 degrees Fahrenheit. If the water is much warmer than that, take frequent drink breaks and get out of the water if you start to feel faint, nauseated, or lightheaded. “It’s the same as if you were running a marathon on a 100-degree day,” says Heggy. “If the water is too warm, your body’s cooling mechanism can be negated, so you have to come out of the water and vent some of that heat.”

The typical commercial swimming pool contains about 20 gallons of urine, according to a study in Environmental Science & Technology Letters. But that doesn’t mean it’s healthy—or safe. In fact, when chlorine reacts with sweat, body oil, and urine it creates noxious chemicals, most notably trichloramine and cyanogen chloride, which can cause breathing problems for those who suffer from asthma and other respiratory illnesses. The moral here: Shower before you enter the pool, and please (please!), stop peeing in it.

Blame your mom—and all the other neighborhood moms—for this one. For years, the prevailing wisdom was that you shouldn’t jump in the pool for an hour after eating because the energy required to digest your food would shunt blood away from your arms and legs, causing you to cramp and, presumably, drown. But several studies have disproved this tired mantra. In reality, less than one percent of drownings in the U.S. occurred after the victim ate a meal. “When you start exercising, your body is smart enough to say ‘We’ll save the digestion for later,’” says Heggy. “If your body really needs to concentrate on digesting a big meal, you might have a slower workout.”

Downing a cocktail or beer before swimming is another matter, though: A staggering 70% of water-related deaths among adolescents and adults were alcohol-related. So feel free to swim after eating, but stay on dry ground if you’re not sober.