We received good advice before we designed our pool. Someone told us, like a boat, "they shrink" when you put in water. Also, I had the same of goal swimming laps. As a result, we went with the largest rectangular pool our lot would allow. Still, it's not large enough for laps. We looked at the swim against the current device, but it was more than we wanted to spend. So my husband found
Swim Tether - Belt Systems for Resistance and Tethered Swimming It works and I love it.
It's my hope this is helpful. Enjoy your new pool!