I swam in a public, concrete pool, with friends, when I was in high school. After high school, I swam in rivers and streams and avoided public pools, because I didn't like the chlorine, but mainly because I was usually near rivers and streams and not near concrete pools.
I haven't swum during the last dozen years because I wasn't near swimmable water.
We moved to central Oregon, and I eventually discovered the local swim and fitness center, which is close and on the way to other, necessary places. I tried the indoor pools and decided that if I bought goggles, the chlorine wouldn't bother me. I bought a card for unlimited swimming for a month.
I hadn't forgotten how to swim, but it did take me a few times in the pool before I coordinated legs, arms, and breathing into reasonably smooth motion through the water. I swam almost every day, and I improved my form and increased the distance I swam.
Saturday morning, I walked into the swim and fitness center. People grouped around the counter. I reached forward and showed my pass to the woman behind the counter. We thanked each other, and I walked into the locker room, changed, showered, fastened my locker key to my swim suit, and walked out of the locker room to the first pool. Lane dividers had been stretched the length of the pool, and two lanes had no swimmers.
I descended the ladder into the end lane and swam down and back twice, concentrating on smoothing out my swimming and on changing from crawl to side stroke to back stroke and variations of all of them. When I swam back the length of the pool a second time, a lifeguard crouched on the concrete was waiting for me. She said, "This lane is just a starter lane, where people dive in. You shouldn't keep swimming in this lane."
"OK." I swam under the lane divider and down the second lane. What she'd said seemed peculiar, since all around the pool "NO DIVING" was painted on the concrete. According to the signs, the only approved diving was from the diving boards, and the boards weren't used when the lane dividers were in place. However, whatever the people who worked here wanted to do was all right with me. They made the rules, and if they wanted to vary them from time to time, it didn't cost me anything.
I kept swimming. More swimmers used the lane I had entered. They seemed very serious and in a hurry. Two people swam down the lane and back, almost matched, stroke for stroke. The next time I looked, they were gone, and the lane was empty, except for me.