Pools may be gross, but your body is pretty great at warding off infections. You're exposed to all sorts of bacteria on a daily basis, the vast majority of which don't make you ill. Pool water probably won't be the thing that gets you. Young children are the ones most susceptible to Cryptosporidium infection anyway, so as an adult you have little to fear. There isn't even a solid upward trend in infections caught from pools, only for those caught from child care centers and cattle, and the CDC itself noted that it's unclear whether the overall upward movement is simply due to better testing. It's probably also true that the CDC's numbers are an underestimate—plenty of kiddos get sick without needing to visit a doctor, and thus won't get tested in the first place. But even so, there are many more dangerous things about swimming pools than the many bacteria living inside them.