From the article
The parasite is a problem in pools is because an infected swimmer can excrete the parasite at several orders of magnitude higher than the amount necessary to cause infection. Cryptosporidium has a high tolerance to chlorine and can survive in a properly chlorinated pool for up to seven days, the CDC says.
And in case you want to go to a public pool to deal with the heat ..
That last one is most important, as 24% of American say they’d jump in a swimming pool within an hour of having diarrhea, according to a survey released last month by the Water Quality & Health Council