If you dive a lot in the pool and open your eyes in the end it will get a little red and it will sting slightly. The popular reason that is adduced to this fact is the concentration of chlorine in water.
However, the origin of this is not chlorine, but the urine of all people who pass through the pool.
Urine and other things
The real origin of the stinging and the redness of our eyes in addition to urine, are other unpleasant substances, such as faecal remains, sweat residues and dirt in general of the body of the users of the pool.
Actually, chlorine is indirectly responsible. When the urine and chlorine are mixed, the combination converts chlorine into an ammonia derivative called chloramine, which has a distinctive odor, and reputation for causing respiratory problems and a telltale effect on the eyes.
However, the worst of all are the faecal remains. People with diarrhea can spread Cryptosporidium, a parasite resistant to chlorine which is the main cause of waterborne diseases.
To avoid these evils, users must be forced to go through the shower before entering the pool. And not to urinate in it, naturally.