I grew up swimming age group in a pool that was 16 3/4 meters long (it still exists and hosts age groupers). 4 lanes. The older groups "graduated" to the 25m pool next to it, so eventually, I got to play in the big pool as well.
I also once swam in a pool that was about 90 meters long (Inselbad Stuttgart - it has since been renovated and downsized). It was not set up with lanelines, so it doesn't count under your criteria. It was an interesting swim regardless.
I also swam in university pools in Germany, which are usually built 20m long to avoid them being used for competitive swimming/racing.
I grew up swimming age group in a pool that was 16 3/4 meters long (it still exists and hosts age groupers). 4 lanes. The older groups "graduated" to the 25m pool next to it, so eventually, I got to play in the big pool as well.
I also once swam in a pool that was about 90 meters long (Inselbad Stuttgart - it has since been renovated and downsized). It was not set up with lanelines, so it doesn't count under your criteria. It was an interesting swim regardless.
I also swam in university pools in Germany, which are usually built 20m long to avoid them being used for competitive swimming/racing.