I went to a cloth diaper workshop at Mothers and Company in West Boylston on Saturday and while there I noticed they had a pool with classes going on. I have no idea if that is within your 'flexible' region though :-)
Not sure where you live, there are a ton in our area, the YMCA's offer them (if they have a pool) I took one at the Waltham Y, the Arlington Boys and Girls club and currently at the Watertown Boston Sports Club.
Not sure if this is convenient for you, but I just signed my son (8 1/2 months old) and I up for swimming classes at the Wayside Racket & Tennis Club in Marlborough as well. I have taken my older son there the past year for swimming classes and he loves it.
Re: Swim Classes