Water Aerobics Anyone?

For some time, I have been looking for a new type of exercise to supplement my walking and strength work.  I tried Zumba, but the side to side dance steps made my knees turn in painful ways.  A few years back I started doing yoga, which I still do occasionally.  But nothing really grabbed me.  My good friend and hair stylist suggested I try water aerobics at the local pool.  Now I do swim in my own pool in the summer, but it doesn't warm up for enough for me until late May, so I thought, "What the heck, I'll give water aerobics a try."  The pool is heated, but I wasn't sure if it would be warm enought for me.  Cold pool water just makes my joints and body ache.