10 Crypto, hot tub bacteria is chlorine-tolerant
Cryptosporidium is a bacterial parasite that tolerates chlorine and can easily survive in a hot tub. It can cause diarrhea lasting for weeks and has no cure so if you contract it you just have to manage it till the disease runs its course.
Crypto is passed through feces and can even result in death. The bacteria in hot tubs is chlorine tolerant and can withstand chemicals for days.