It's a daily occurrence at public pools — swimmers take the plunge without giving themselves a proper wash beforehand.
"People come in and they put their body in the shower for maybe 10 seconds, if that," said Laura Seaboyer-Sankey, a manager at Centennial Pool in Halifax.
"I mean we see it all the time, people come out with wet spots on their bathing suits, but it's obvious they didn't shower."
A new survey on swimming hygiene conducted for the Water Quality and Health Council in the United States found more than half of adult respondents "seldom or never shower before swimming" in a pool.
Seaboyer-Sankey believes people don't shower because they don't know why they're supposed to.
"I think the misconception is, is that people are showering to get rid of the scent or get rid of just the body oils, when in reality it's more of a health and safety issue, and we're really trying to get rid of the fecal matter, the stuff that makes you sick."
People in the pool business are most worried about the parasite cryptosporidium, which can cause gastrointestinal problems when swallowed.
Unlike many other microscopic organisms that can be killed by a pool's chlorine or other chemicals, "crypto" can tread water for a long time.
Steven Lam co-authored a research paper on cryptosporidium outbreaks associated with Canadian swimming pools in 2014 when he was a student at Guelph University.
"Cryptosporidium is special, it has an outer shell which makes it resistant to chlorine and heat, and so it may take up to 10 days to kill."
In the U.S., the Centers for Disease Control and Prevention said the number of crypto outbreaks at swimming pools has doubled since 2014.
But in Canada, Lam said, cases aren't documented as well, so it's hard to tell how many people are getting sick after swimming. He also sympathizes with swimmers who don't understand the reasoning behind the shower signs at pools.
"I think we got our public-health messaging a bit wrong, because at showers it just says please rinse off or something like that, it doesn't say please shower with soap and that idea, and that's what's needed to get rid of crypto."
Another guideline not being followed is aimed specifically at people who have recently had a gastrointestinal problem.
The Water Quality and Health Council said one out of every four adults it surveyed said they would swim within one hour of having diarrhea.
Lam said that's way too soon.
"Some sources recommend even two weeks after you have diarrhea, because you may be still shedding these germs."
For that matter, what happens when someone has an "accident" in a swimming pool? Contrary to popular belief, pool officials rarely drain the water, according to Seaboyer-Sankey.
"At our facility, if there's a foul, the lifeguards remove everyone from the pool and the ball starts rolling from there, the chemicals are added and shocking the pool."