https://www.cambridgema.gov/-/media/Files/DHSP/Recreation/programbrochures/warmemorialbrochure.pdf#page=18

The War Memorial is the city's public swimming facility. They have a 25 yard pool. The current (Fall 2022) schedule is found at the URL above. Looks like evening lap swims are what is available.

Near Porter Square is the Somerville pool. They also have a 25 yard pool. The current schedule is found at the URL below: https://somervillema.myrec.com/info/facilities/details.aspx?FacilityID=13622. Looks like morning lap swims are what is available.