Archie, the aforementioned NovaFitness is in zone 10 (trams 2 and 3) and has a smallish pool. You don’t have to have a membership, but individual entrance is something like 30chf. It's not *at all* a highly trafficked pool and you will often find you have the water to yourself. Open all year long, EVERY DAY, even on holidays.
Stop by and you can take a look at it.

The big Hallenbad is a hellish place that you will *undoubtedly* bump into people. When I went there I tended to leave more stressed out and pissed off than when I came in; people erratically swimming, standing and chatting IN the swimming lanes, etc.

Good luck