Chlorine does not kill all the nasty things
Unfortunately, most people have a false sense of safety when they’re in a swimming pool because they assume that chlorine kills everything. In reality, it does not. Swimming in a communal bathtub basically means that you are sharing all the germs in the water with all the people in there.
Research on more than 630 nationwide outbreaks of illnesses caused by viruses, bacteria, or other nasty floating things in bodies of water revealed that almost 80% of outbreaks were linked to water from wading pools, hot tubs, and swimming pools.