That's the conclusion of a new study from Scotland's Aberdeen University, where researchers found only two-fifths of couples drink water after making love.
"Sweating, flushing and panting" — which describes more than a few lovers — "are all signs that the heart rate is faster, meaning that the body is reacting in the same way to sex as it does to other cardiovascular exercise," according to fluid balance and hydration expert John Leiper.
More than 90 percent of us have a drink after running or a workout at the gym, according to Leiper's research, so it makes sense that equally strenuous sex also warrants some rehydration.
And here's some added incentive: Dehydration can put the kibosh on future canoodling. Dried-out lovers are prone to fatigue, lethargy and headaches, not to mention dry mouth. And not only does a post-coital glass of water prepare you and your partner for more loving, it's a lot better for your body than the cliched after-sex cigarette.
Sex is supposed to be good for your health, after all. It can be as strenuous as a three-mile run (and more or less fun, depending), burning as many as 360 calories an hour. The amount of energy your body burns also depends on your, er, degree of vigor.
But even if you don't break a sweat during sex, you could still be draining your body's H20.
"As we go about our daily activities, we continually lose water — even when we are not visibly sweating" Leiper said. "When we take part in exercise or sexual activity, this water loss increases and we need to replace it to prevent dehydration."
A quick, unscientific poll suggests post-coital water consumption does indeed vary.
"My water's usually nearby — you have to be prepared," says Rochelle from Florida.
Theresa, from Tennessee, has her system all set up. "There's always a bottle near my bed," she says. "Water. No ice. Not too cold."
"I guess I have been thirsty, but water never crosses my mind," says Dave, from New Jersey. "The shower doesn't count, does it?"
No, Dave, not unless you drink the shower water.
— Sky News contributed to this report.