Family holiday is meant for unwinding, sightseeing, or even diving into a good book, but according to research, one of your kiddos' favourite activities — swimming in the hotel pool — isn't without a few truly gross risks.

In a recently updated report that was originally written in 2015 [1], the centres for Disease Control (CDC) warned parents of a major pitfall that's associated with hitting up the pool while on family vacay: cryptosporidium, a microscopic parasite [2] that causes diarrhea and other stomach issues in unlucky swimmers. The scariest part about cryptosporidium — or Crypto — for short? It can withstand chlorine.

And unfortunately for families trying to enjoy a week or two away, hotel pools, specifically, are the most notorious offenders. The original report found that one in three waterborne disease outbreaks that took place in the US between 2000 and 2014 occurred in a hotel pool or hot tub. And as you probably guessed, cryptosporidium was the main culprit.

According to the research, 493 disease outbreaks were reported over the 14-year span resulting in 27,219 people getting sick and eight people dying. Of the total number of outbreaks, the CDC found that Cryptosporidium was responsible for a whopping 58 percent of the number of outbreaks that were linked to pools. Legionella and pseudomonas, two other form of bacteria strains that live in the biofilm (the layer of gunk on a dirty pool), followed suit.

Michele Hlavsa, a registered nurse and chief of CDC's Healthy Swimming Program said back in 2015 that there are a few precautions parents should be mindful this Summer before letting their kiddos launch into cannonballs.

"Swallowing just a mouthful of water with crypto in it can make otherwise healthy kids and adults sick for weeks with watery diarrhea, stomach cramps, nausea, and vomiting. Chlorine cannot kill crypto quickly. We need to keep it out of the water in the first place. Don't go into the water, and don't let your kids go into the water, if sick with diarrhea."

Looking for an additional ewww factor? Hlavsa said that believe it or not, your eyes turning red because they're irritated by chlorine is actually just a myth — the real reason is much more disgusting.

"Have you ever had red, bloodshot eyes after swimming in a pool? It's not the chlorine causing them to redden and sting. It's urine mixing with the pool's chemicals [3], Michele told Today.

"The nitrogen in the urine combines with the chlorine and it forms what's known as chloramine and it's actually chloramine that causes the red eyes, she said, adding that, "It's not chlorine's job to clean pee from a swimming pool. Its plate is full with E. coli and other germs. Once people start adding pee, poop, sweat, and dirt to the equation, it starts to try to tackle those instead, leaving it with little energy for anything else."

Yuck! Looking to keep your little ones as safe as possible without writing afternoons spent swimming off for good? Follow these CDC-recommended tips [4] to minimize their risk of getting cryptosporidium:

• Do not, under any circumstances, let your kids swallow water or blow bubbles.
• Take young children to the bathroom frequently and don't overestimate the strength of a swimming diaper — they're not infallible as far as leakage is concerned.
• Don't let your kids swim if they've come down with a case of diarrhea. If crypto is the cause, wait two full weeks until the diarrhea has passed to let your child back in the pool.
• Check the pool or hot tub's inspection score before going for a dip.
• Test the pool's chlorine levels with throwaway strips [5].