Exercise is very good for you.
But I would have doubts about getting any wounds wet with pool water. Risk of infection.
Shower water may be different.
One of my Breast surgeons insisted that I didn't even get wet in the shower.
My Plastic surgeon didn't mind shower water.
I think pool water wouldn't be clean enough.
Is, or could the pool to walk in be so shallow as to not get wet above the hips/waist?
I'll be interested in the answers you get, from BC Nurse and the Surgeon.
I think that the same will apply during Radiotherapy.
Some people experience 'burns' and skin breakdown. An infection could be very nasty.
I had 5 weeks (25 sessions) R/T. I had no skin damage. I was very lucky.
Where I had R/T they applied Mepitel (a specific plastic looking dressing) over the treatment area.
Ask more about that later if you want.
Wishing you all the best with everything.